If you want to go to Provo for reasons in addition to law school admissions, and it wouldn't be too much wasted time and energy, then go for it. But law schools mostly just care about GPA and LSAT when it comes to admissions. I don't personally think it'd be worth the trouble to transfer if the only reason you'd be doing it is for law school admissions. Soft factors can count for a lot, of course. But of all the possible soft factors, I think that where you went to undergrad is pretty close to being the least important one.
That said, I don't know anything about BYU Law specifically and how much going there for undergrad, given the whole religious element, counts for anything. If I were you I actually might just email the law school admissions office and ask them. You'll probably get a canned answer, but you might get some meaningful advice and you don't really have anything to lose by asking.
Oh, and just as an aside, are you really pre-law? Like officially?