There really isn't. SMS isn't dependent on having a BlackBerry data plan, it is simply an issue with the older iDEN BlackBerry devices to not be able to send mobile-originated SMS. The only one I know of that can send SMS is the new 8350i. The reason that you can't do it from the e-mail application on the phone is that you don't have a BlackBerry data plan, which, as you know, is impossible on Boost.

This device is very old, and I'd recommend getting an 8350i if you want to use any modern mobile services.