I'm in Canada, where there are fewer guinea pig-savvy vets around. I generally would look for a vet that specializes in exotics, and then would ask them how much experience they had in treating guinea pigs with specific questions: How often do they trim teeth? How often do they do surgery? What methods of anesthesia do they use (it's much safer to use inhaled anesthesia with small animals, so if they were not doing this, it would be a red flag to me.) What antibiotics will they use (or not use) in guinea pigs (due to their gut flora they cannot have certain antibiotics but can have others- if a vet wasn't aware of this it would be a red flag.) I also ask how much experience they have with related animals (for instance, my vet sees more rabbits than guinea pigs, but certain issues, like abscess or dental problems, are common in both species.) I've been very lucky that I've managed to find a great vet, though I do have to drive half an hour or so to get to him. But he's well worth it! I lost a pig to a problem that was not treated properly when I was too naive to know better, so I'm now really aware of how much difference vet experience can make and am really happy with where I am now as far as vet care goes. He's gotten Sundae through some serious medical problems, for which I am extremely thankful, as I don't think she would have survived with a less experienced vet (and a less uptight owner! LOL!)