I am at Texas A&M right now and May's Business Schools is one of the 10 Top Business Schoools in the country...I think they might even be in the top 5.
I've heard of Mays, but it isn't a top 10 business school. It was ranked 29th by USN&WR.
Regardless, I'm not a big rankings buff anyway. And with business schools, other than the big nationals (Wharton, Sloan, etc.), most MBA programs make their biggest footprint locally. Anderson (UCLA) kicks open more doors for you in LA than Fugua (Duke) would, even though Fugua is considered by most to be a better program. If you're planning on practicing in Texas, Mays would be tough to beat.
Would that change your advice at all?
No. MBA value ages quickly if the degree isn't put to use. You keep the accounting, finance, marketing, etc. knowledge, but you can learn this anywhere. The real benefit of MBA is the contacts/networking and the ability to integrate the material you've learned into real world scenarios.
I wouldn't advise someone to do an MBA unless they had a background to build on and an environment to expand on. Doing a one year MBA in the middle of med school always strikes me as the worst of both. The only reason I could see doing it is if you felt you'd never have another opportunity. And you'll have better opportunities.
Just my $0.02. Regardless, I hope whatever decision you make works out. After two years of med school, business study would probably be a welcome change....