There are usually some taxis in the theme park parking areas, but you may need to ask/look for them. I've seen taxis from time to time at some resorts (GF, CR, Poly), but not at others (CSR, WL). I'm sure the Bell Captain can call one for you at the resort if there is not one waiting.
We were there in Nov. and didn't see lots of cabs around, but there always seemed to be some available just about anywhere we went. DTD had lots available, especially throughout the evening. There were always some at every theme park.