I'm assuming you don't have a boat or kayak, correct?
San Luis Pass:

If the tide is coming in strong the flats north of the marsh island can be good too. Find the guts and trout will be waiting to ambush bait coming in on the tide.
Christmas Bay (east entry point):

Fish the south shoreline and work your way east to the channel in the NE portion of the picture. That's Churchill Bayou. Watch your step as there are stingrays and you need to mind the boat cuts.
Christmas Bay (west entry point):

Fish the south shoreline west. Lots of oyster reefs toward the old ICW (channel to the NW of this pic) and pretty clear grass flats on the south shoreline. Again, watch for stingrays. There are fewer boat cuts here but the water gets relatively deep (4'-4.5" near these oyster reefs).
Tide predictions (use the Christmas Point prediction):
http://www.saltwatertides.com/dynamic.dir/texassites.htmlYour best bets are going to be the couple hours ahead of a rising or falling tide.