Alos, when you say your PC came with secure boot enabled do you mean to say it was enabled and you couldn't change it's settings to accept linux as an alternative OS but you were able to turn it off to let both Operating systems boot? So you could get into linux eventually without problems, but to do so you had to lose the small security advantage which secure boot sometimes gives by turning it off entirely.
Well, back in 2013, it was doubtful that Linux Mint even has keys needed to run Secure Boot. Red Hat was one of the select few that did.
Yes, Secure Boot was enabled when I received it with the Dell OEM or 'Home' version of Windows 8 installed. Before I even installed any other OS's. I had cloned that OS with Macrium Reflect, along with it's other needed GPT partitions, to a 120GiB SSD, though had to disable FastBoot and System Restore prior, as well as run Extended Disk Cleanup before it could be done. Afterwards, was only using half of the space on that 120GiB Samsung 840 EVO SSD, and for about a month ran it that way, with Secure Boot enabled. Credit goes to badr0b0t for this one, I'm sure he recalls. 
However, I soon got tired of not being able to run Windows 7 on my best PC, and ordered another SSD for it. It was then that I realized Secure Boot had to go, as well as the GPT installed Windows 8. The recovery media wouldn't allow me to reinstall to a smaller than original drive, and even if so, would have been in GPT format.
One thing that swung in my favor was that Dell is one of the few OEM's who provides a reinstall DVD w/out the extras (nor drivers) during the initial warranty period at no charge, they know many installs smaller SSD's. I ordered this at like 11AM or so, and it was here before 10AM the next morning (have 24 hour next business day service). This is what allowed me to, as you made a point of above, to install in MBR mode, so that I wouldn't have to switch between Secure Boot & MBR, nor would have I done so anyway, Windows 8 would have went out the door had it not been for Dell shipping that DVD.
The original HDD was placed in a box that another was shipped to me in, with the OEM installed OS intact, just in case warranty service is needed. I'd just remove my drives, re-enable Secure Boot, and reinstall the OEM supplied GPU & RAM, it'd be in OEM condition for the tech to diagnose & repair. Sometimes, the unit must be removed from the premises for repair or replacement, and there's no way on this earth that I'd give them three SSD's & 32GB RAM, plus a better HDD than came with the unit.
Actually, Linux Mint was the last OS to be installed on the PC, and that was a couple of months post purchase.
Anyway, with the keys or shims included in many Linux distros today, and as long as you have no desire to run Windows 7, you won't have to go through the troubles I did. You will have to learn how to install Linux in the GPT fashion, which I didn't, however I'm sure there's plenty who has & can assist. GPT is preferred over MBR & has advantages over it. I would have preferred to keep Secure Boot & GPT like it was, unfortunately Microsoft, despite the fact that Windows 7 carries the corporation & units as well as licenses are still moving fast, refuses to port Secure Boot to that OS. So I did what I had to do to have all OS's installed.
Seeing as this tyoe looks reasonably good has anyone had experience running linux on it or similar models, I can't find any direct reference to linux on this exact type by searching google, so couldn't find any clearly relevant results with the serahc term "Linux on HP 15-g260sa".
You may find some information on the HP forum as to those who have installed Linux on these units, however don't expect any assistance from them. Before installing Linux onto the new computer, be sure to create your recovery DVD set, you may not be able to afterwards, nor will the Recovery Manager work as out of the box. Just in case you decide to sell it later on, or in the event that a new HDD is needed. It's better to have these & never need them than to need & not have the set. Your warranty doesn't cover a corrupt or broken OS, just the hardware.
As is with the computer you now have, you should test in Live Mode first, though with new hardware, I don't expect troubles. It's just that some or most of the OEM functions won't work as on the OS it ships with.
And regardless of your decision, be on the lookout for any updates that may trigger an auto Windows 10 upgrade in the background after release. Microsoft is desperate to make Windows 10 a success, even if they have to underhandedly install the OS onto consumer's computers. There has been a couple of articles that suggested that MS may include Windows 7 consumers into such an update, though at this point, it's talk. As the date nears, I'll be watching every update closely, Google searching all that has to do with the OS. I caught them twice trying to slide 8.1 in on me in that manner already & have reported that in other areas here.
There is also another possibility if you decide to hold out, this makes the 2nd Windows release in a row that MS has either heavily discounted, and in the case of 10, give away. OEM's whom have remained loyal to Microsoft has to be getting edgy, forcing some to look in other directions, or at least consider. They have many millions of employees globally & with computers as reliable than ever, they're not in a good position for at least the first year, to cash in on the success of Windows 10. The majority who jumps on the wagon will so so at no cost.
What are these OEM's going to do, sit back & wait until MS starts selling OS's again? Sure, some will be sold, but not in the numbers that Windows 7 units did. They'll have to find a way to sell computers, be it with or without Windows on them, or layoff many employees. There are smaller Linux system builders, yet they're way too pricey due to lack of component costs. The larger OEM's hold the advantage, at some point will have to make a decision, hopefully distributing computers with mainstream Linux OS's installed. Acer & HP holds a contract with Walmart, and Dell is in the mix also. What better retailer on the planet is there to mass market Linux OS's through?
Just saying, Microsoft isn't the only corporation with ideas, these massive OEM's has to have a 'Plan B' in place to keep the factories moving. Chromebooks are already one option for some. Dell has made two attempts to push Ubuntu, maybe they should throw Mint in the mix?
Cat