Lynnandcarol's routs are the way to go. When you cross into Texas stop at the Texas Visitor Information Center, exit right just after you cross the Sabine River(state line). Pick up free Texas maps and information guides and camping information. Plenty of room to park your rig.
When you get to Winnie exit I10 onto state hwy 124, past High Island you will turn right at the dead end onto state hwy 87 to the Boliver ferry just past Crystal Beach. When you get into the ferry line , get out and turn off your propane. The ferry is free and plenty of room for your rig.
There are 2 ways to get out of Galveston, north on I45 to state hwy 6 to Alvin and left on state hwy 35 to Rockport, or FM 3005(Galveston Island beach road) west thru Jamaca Beach to Surfside Beach. There is a toll bridge to get across San Luis Pass and off of the Island, $2.00. Right on state hwy 332 across the GICW bridge, left on 523 at the light thru Freeport to state hwy 36, right to state hwy 35 and left to Rockport.
All the state hwys are good and safe with great views and lots of small town Texas charm. Enjoy the trip.
The roads are good, wide shoulders. I get confused about which lane to be in for the turn in Jourdanton so watch the road signs carefully. You have to watch out for small town South Texas traffic, they have the right of way( they think.)
Have a safe trip,
You may want to try Padre Island National Seashore. Not quite to the valley but still warm and great beach camping. Fresh water available and a limited supply of food in the visitor center store.
You can camp on the beach in Port Aransas on Mustang Island for 3 nights for $12. beach parking permit. Lots to do and see in Port A.
When you enter Texas stop at a visitor center and pick up a camping guide. Move off of the interstate to Texas state highway 35 as soon as possible. It follows the Gulf from Houston to Corpus Christi with plenty of camp sites on the water.
No problem getting on the Cameron Ferry in your MH. LA82 is 2 lane and in pretty good condition, The Cajun communities along the way are the main attraction. Check out Abbyville RV park in Abbyville, not fancy but nice. Visit Avery Island , home of Tabasco pepper sauce, and the other attractions around New Ibera. Get a Cajun 7 course dinner(a pound of Boudin and a 6 pack).
Hope you enjoy the area,
From Jefferson take hwy 49 west towards Avinger, about 5 mi take a left at the Y on hwy 729 towards Lake O the Pines, about 5 mi take a left on hwy 726 towards the dam, when you see the lake look for the right turn into the park.
Nice park, great fishing.
I B Magee Beach park is a county owned park just down the beach from the ship channel jetties in Port A. You can fish from he jetties and do about as well as a nearshore boat. The best surf fishing in Texas is in Padre Island National Seashore located just South of Port Aransas, which is on Mustang Island, and Corpus Christi on Park Rd.22. an extension of South Padre Island Dr. It is dry camping but great fishing and beach combing/shelling.
The offshore party boats are all about equal. They are located along either side of the City Harbor. The big factor is the weather offshore.
Why don't you come on down for a short vacation before Jan. Look the area over and find a place that fits your desire. There are 100's of parks in the area, all with diferent attractions. Rockport is only one of the towns in the area that is on a Bay, try Portland, Aransas Pass, Port Aransas( on the Gulf), Port Lavaca, Placos, Port O'Connor, and Matagorda or some of the smaller communities in between, even Corpus Christi and south in Rivera/Loyola Beech, Port Mansfield, and on into the Valley. In fact you could probably spent 3 months just moving around from beach to bay to woodlands to big city to hill country to Rio Grande Valley. As an ex-Okie I hope you find what you are looking for.
Last year you just hit a warm spell with still cold water, we had seafog and haze untill the water temp caught up with the air temp. Here in the coastal bend it was usually gone by 10:00am and the rest of the day was sunny and warm.
Your plan to float South sounds great. Don't miss Goliad State Park, Port Aransas/Mustang Island, Padre Island National Park, Texas State Aquarium, Goose Island State Park when you get to the Coastal Bend.