Orlando, 2 weeks... Transport questions?

Me and my boyfriend are going to Orlando for 2 weeks in October. We are staying in the Pop Century Resort. We hope to "do" Disneyland, and maybe take a few days out to go to Busch Gardens, Sea World and Universal Studios. Is there public transport to take us to these places and how much will it cost (approx)? I browsed previously asked questions and it seems like everyone suggests hiring a car, however I fear this would be well out of our budget. Thanks.