Practicing lawyer here who worked for the DOJ for a while . . .
I completely agree of the two offers you mentioned, doing UMass with a Social Thought and Political Economy major (at least to start) is great. You really do not need to do something specifically legally related in undergrad, if anything that is a negative compared to a more general degree. Anything reasonably rigorous that interests you and where you can get good grades is a viable choice, and if I was going to give any specific advice I would just look for majors where there is a lot of difficult reading and writing.
I also think it is impossible to really know in advance what sort of law you will end up wanting to practice. In fact most of the civil law world is very unknown to people outside the profession, but there are all sorts of areas which can be intellectually satisfying, lucrative, and so on. Like some of the happiest attorneys I know do tax–I think people assume that must be boring, but they are basically doing a form of creative business consulting to help their clients optimize their tax posture. Very fun.
Community college to save on costs is also a perfectly viable choice. I know that may not be your ideal four-year college experience, but here is the thing–fast forward a bunch of years and you are looking at your first job opportunities out of law school. You would love to take some sort of cool public interest or government job where you would immediately get lots of responsibility and skip past the junior associate grind at a large private law firm (you can always lateral back into that world as a more senior associate later, although who knows, maybe you will make a career in public service).
But wait–you have this huge overhang of student loan debt that needs to be serviced. So you feel like you really can’t take the cool job, you have to go into the private firm grind so you can make enough money.
This dynamic is very common and it contributes to so many JDs quickly burning out and exiting the profession. And so you don’t want that to be you if you can at all avoid it.
OK, so back to the beginning–if going to CC for a couple years before transferring can save you a bunch of student loans, that is no small thing. I am not saying you have to do it, but I personally think something like the federal loan limits are a pretty good estimate of how much undergrad student loan debt is reasonable to service:
https://studentaid.gov/understand-aid/types/loans/subsidized-unsubsidized
If you would need a lot more in loans than that to make going to a four-year college right away a viable choice–like I said, just think carefully about how that could contribute to limiting your practical choices in the future.