Hi Bug_Key : )

If you would like to read about humingbird migrations, here's a good link and website to start finding out more info.

http://hummingbirds.net/migration.html

Another website, part of the USGS, lists 2 hummers for the keys.

HUMMINGBIRDS Sp S F W
Black-chinned Humm o - - -
Ruby-throated Humm u r u u

o - occassional, u - uncommon, and r - rare

Here's a link for that info:
http://www.npwrc.usgs.gov/resource/birds/chekbird/r4/flkeys.htm

I suspect you'll see other species visiting from the Caribbean islands from time to time.

If you see 'em, post what ya see : )

Good luck and happy humming : )

Here is a link that might be useful: Florida Keys Birds List