Florida, so likely all the waters except maybe the Spheal and Piplup families and Lapras unless they wind up at Disney or the Miami Seaquarium. The beaches would be overrun with Wingull and Pelipper and our local beach has a sea turtle re-nourishment program so count Squirtle and Tirtouga high on the list. Likely, too, all the electrics except Blitzle (save zoos, etc).
We have thriving industries in both cattle (beef and dairy) and equestrian so expect to see Tauros, Miltank, Bouffalant, and Ponyta on farms along with the various dogs and cats (meowth, growlithe, poochyena, etc) endemic to those areas. Tepig and Spoink might show up on someones farm or having gone feral , but they'll be uncommon-to-rare if they do.
Count in an assortment of city-birds including starly, pidove, et al, the bats, the deer, Mandibuzz, the ducks, Braviary...pretty much anything non-marsupial (no Kangas), non-ice (Lapras, Weavile, Vanillite, etc), and non-restricted to zoos (Zebstrika, the apes, etc). Anything not domesticated will be running wild or feral and what's not in an inhabited area (developed or rural) will likely wind up in the swamp so include poisons and the gators (totodile and krookodile).
Very Common's would include anything Sun-dependant: anything with Chlorophyll, sun stone evos, leaf stone evos, solarbeam carriers, etc, as well as Rain abusers (pretty well covered by water and electric, above) and water stone evos. Expect Exeggcute to be exceedingly common as we are actually "The City of Palms" (most of our streets are lined up both sides by coconut palms). Bet on seeing Raikou down here as well as we are known as the Lightning Capital of the World in addition to being the Sunshine State.
edit: yeah I actually spent some time thinking about this...especially once my 7 year-old called our housecat a Persian and our dog a Poochyena
And how could I forget the bugs? All these years waiting for a mosquito pokemon and I forgot the stupid bugs....