Seconding Sonja’s advice a beginner adult could as well start out from an Alto recorder.
IMHO, however, the lower you get, the poorer plastic sounds compared with wood: correct as soprani, acceptable as alti, yucch as tenor.
I also believe that advising against wood is prejudice: most factory-produced wooden recorders, i.e. the most affordable ones, are made of wood (often maple) impregnated with resin, or durably coated with hard varnishes. They’re also extremely consistent from sample to sample.
Also, the “recorder sound” may be more typical of baroque (bore, not fingering as opposed to German/modern). Renaissance recorders have a more open sound, greater range. There’s a revival of this wider, less conical bores, with new developments like Adriana’s Breuking) “Dream recorder”, available about anywhere in soprano, and often alto. Looks cool for Renfairs, too 
See for description http://www.mollenhauer.com/shop/de/dept_23.html
and for source, price, try http://www.susato.com/mollenha.htm (search for “Renaissance” or scroll to the end of the page).
PS: Edited to ad the guy Paul Busman down there knows recorders–and whistles!–better than I ever will.
He makes good whistles and plays good recorder 
… so if a “got wood?” fine whistles maker tells you a Yamaho alto plastic recorder is ok with him, you can trust him.
Though, there might be a cunning, Florentian (Florensick?), Borghese! ploy here: advising the crappiest cheap far-East recorders, so you keep a taste–and budget!–for high-end whistles. We don’t want you to spend all your whistle money on expensive Bressan things, after all…