I have the same deal as you I think. Sad to say, I have not found a solution.
I am t-mobile USA without a data contract. I use wifi for everything. My contract allows for unlimited MMS, but MMS only works with mobile data turned on. So, I am stuck with sending MMS only when I have wifi on and mobile data on. When people send me an MMS I have to turn on mobile data and ask them to resend.
On a side note, same contract, my daughter has a mytouch 4g slide that can send and receive MMS without mobile data turned on. She is on Gingerbread and I am on Jelly Bean. I have tried copying her APN and nothing has worked.