Be careful launching there. The ramp is pretty short. We launch RaheemX's 16' Jon boat in there, but I'd never put my 20' cc in there. There is also the Dickinson Bayou ramp under 146, but the guy at Marburger's told me today that there have been a lot of cars broken into there lately.
The best ramps in the area that I have seen are:
Galveston Yacht Club $10 launch fee!
Texas City Dike $5 to get on dike.
Clear Lake decent ramp but free
the ramp at Hwy 3 at 517 is pretty good and it is usually never crowded and free. it is usually where i launch to fish dickinson bay. it is about a 10 min boat ride to the Hwy 146 bridge and another 10 mins to the flood gate of Moses.
I've launched there 100 times and never had an issue
I've launched my 36ft contender there with no issues. If it's a low tide with a strong north wind,you might have some trouble getting it it. It's usually a easy launch.