I think the prevailing theory is that Hollywood fires a lot of digital artist's imaginations out on the west coast moreso than architecture, and so there are less architectural digital illustration studios out there than on the east coast. Whether that is my east coast myopia, or is true I just don't know - I do know there are tons of super talented artists.
by default you'll come up with a preponderance of traditional artists but you might try:
http://www.asai.org/Search
just type in the number of results you want and a central zip code, and it'll give you a list in radial distance. Pretty handy, and you can list only digital firms if you want.
you can also hit the yellow pages.
off the top of my head...
Heartwood Studios: hwd3d.com
?Michael Sechman: msechman.com - dead link
?View by View: viewbyview.com
Screampoint: screampoint.com
Robert Frank: rfassoc.com
crazy homeless guy: phase22.com
Transparent House: transparenthouse.com
Or, if you're looking for bays, you might try beautiful Narragansett Bay, the jewel of New England, and look at studioamd. Similarly if you meant the pristime shores, and year round beaches of Tampa Bay, they have an office there too.
Good Luck!