Only singles now I know that in 2004 they did have double, but I guess they must have decided they were too cumbersome or something because when we went last year they no longer have them, and when we asked about them, they looked at us like we had a horn coming out of our forehead, lol.
I don't know how long you'll be there, but if it's more than one day and you know you'll need them every day, and you don't have the disney visa deal...I suggest getting a multi-day pass. You do NOT save money, but you don't have to wait in the often long line each morning. Just bring the receipt for that day (they give you a little envelope, KEEP that and bring it each day) over to where they give out the strollers, they fill out a nametag for you (unless you kept the one they give you the first day), and there you go. Saving time can be as valuable as saving money!