I just got back from my vacation in NYC last week. I made a trip to the plant district while we were there. We picked up a huge cluster of a bromeliad species I haven't identified yet for $15 (there are about 8 plants in the cluster). We also got some tillandsias. Besides that, however, there really wasn't anything that interesting to me. Being as though orchids are in vogue, there are huge amounts of them there...but really not that cheap. You can do much better for the same plants at Home Depot.
There is a sea shell store at South Street Seaport that sells much better and bigger tillandsias than the ones we got in the plant district for less than $5.
The indoor conservatory at the New York Botanical Gardens is INCREDIBLE, and a visit there will give you many ideas on how to grow different tropical epiphytes. If I lived in NYC, I'd have a membership there and one with the Wildlife Conservation Society to get into the zoos (NY Aquarium, Bronx Zoo and Central Park Zoo have dart frog exhibits).
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David Knight
Tempe, AZ
D. imitator
D. leucomelas
P. terribilis
D. azureus
D. tinctorius (Alanis)