All the major ones (and some of the not so major) are available at the POP airport. I would only rent from one of the major rental companies (National, Hertz, Avis, Alamo, or Budget).
Since the rates vary depending on when you plan to rent, use one of the many search engines (travelocity, orbitz, etc) to find the best rate. If you are concerned about price, you are better of renting away from the airport, you will save the 7% airport tax. Most times you can return the car at the airport, even if you've rented in town.
Regarding telephone numbers, here's a link to the yellow pages.
http://english.dr.superpages.com/li...&S=DR&NA=&PM=000c7937&LC=40&PI=1&MC=1&CB=&PP=
