Wire - Call Houston Metal Stripping at 281 367 4037. I do not know if they sandblast but they do have acid tanks and do media blasting. There are some other places that may be able to help you out. To find them do a yahoo search for "Sandblast*, Houston" and make some calls. The last time I investigated this I found a couple of places on the east side of town that would work with me. Also search for "Metal Stripping, Houston" as it might turn up other options.
To blast my trailer I rented a 175CFM compressor for $75/day and used a friend's pressure pot. It made a hell of a mess but I was able to clean it up before the neighbors got too [censored].
If you do it yourself be sure to use safety gear. I would offer my assistance but I have been there and done that already.
If the frame is not too bad you can use a knotted wire wheel on a grinder to get most of the problem areas and then use a small siphon blasting set up (Wal-Mart has them) for the areas you could not get to.
