It's not mms but I've been sending my pics this way. This works if you have picture mail.
1) Set up a picture mail email. ie.
2) Set your BB camera to small 640 x 480, bigger takes a lil longer to send
3) Take picture
4) Send pic to your pm.sprintpcs.com address you created
5) You will be notified at your BB messages that you have a picture
6) Open the message and forward to whomever you want to send it too. This is where it works similiar to MMS. You put the number you want to send it to and send it - like text message.
Seems long but actually once u take pic and send to your email and then forward it, it's really short...less than a minute.
I hope this works for you as it does for me.