I actually don't have a 50bmg and I don't have any guns as my wife forbids it. However, I did buy one for my Dad.... Sometimes, it is easier to circumvent the Mrs instead of colliding with her head-on. If you're looking for a 50bmg friendly range, the closest that I know of is Tac Pro in Mingus, TX.
Prairie dogs?! I don't think anything will be left to eat after getting shot with a 50bmg! You'll probably have a fine red mist after the prairie dog gets shot.
I purchased for my Dad the Serbu BFG50. It is inexpensive ($2200+) and it is a 0.5 MOA gun, per other users' posts on the Serbu forum, the THR forum, and other forums. It also has relatively little recoil compared to other 50 BMG's. It is a single shot rifle. Some people don't like these and favor the semi-autos. To those people, I ask, "At $5 a shot, can you really afford to shoot a 50 BMG semi-auto?" Besides, have you ever seen a 50 BMG ammo round? It is roughly 6 times bigger than a 30-06. With THAT much more recoil, do you really think that you can visually re-acquire a target fast enough to take advantage of the semi-auto's theoretically faster 2nd shot? Unless you are a millitary pro that practices all day long, every day, I seriously doubt any amateur can actually take advantage of the faster rate of fire of a semi-auto 50 BMG. I certainly can't.
The following is not the pic of my gun (I don't own any, remember?

), but it is a pic of the gun:
A Barrett "light 50" (M82A1) costs $8650 for just the gun only. For that price, I could buy a Serbu, a scope, a lifetime supply of ammo and still get change back!
Serbu BFG50: $2200
Bushnell Elite 3200 scope: $220
1000 rounds of Barrett M33 Ball ammo: $5000
Total: $7420