Allergic reaction is a VERY good reason to discuss this with your provider, and a great reason in terms of convincing even a conservative OB to perhaps modify their position of standard procedure. And since some antibiotics will lose their effectiveness if you've built up a tolerance that's another topic to bring up. It's a good thing you've got some time to plan though, since an allergic reaction could be a really unhappy surprise!
From my own experience, I have a complete tolerance to the "caine" drugs...it seems to be a family thing, but they just don't work on me. I had planned a nice natural birth so when I wound up with a c/s it was a bit challenging to explain to the hospital staff that the local numbing meds they normally use wouldn't work...they were great, and we found some drugs that were just as safe but which DID work, but it would have been better all round if I'd been able to discuss all that before labor started!
I'm sorry the birth climate in your area is so ick...you probably have already, but check with ICAN (either your local group or the national email list) to see if there are any VBAC care providers or options in your area. And local midwives, doulas, and LLL leaders can often point you towards the more VBAC friendly OBs (or at the very least natural birth friendly OBs who will make your c/s as close to a natural birth as possible) even if they can't take you on themselves.