IAH to Webster is nearly a straight shot on 59-South and I-45 / Gulf Freeway- South. Exit the IAH airport via Will Clayton (east) rather than JFK (south). Take 59 South to I-45 South. There are alternative routes to get to I-45, but unless there is a major accident along this route, it is probably the best way. Traffic will come to a crawl on I-45 / Gulf Freeway once you get to the South Beltway. If you have an additional passenger, you could probably bypass some of the traffic at that point by using the HOV lanes.
Webster to South Post Oak (if you mean near the Galleria Mall by the 610 West Loop) is easiest to reach by taking I-45 / Gulf Freeway north to the 610 Loop westbound and exiting around San Felipe. (The Galleria Mall is at Westheimer and Post Oak just one block west of 610.) Don’t confuse Post Oak and S Post Oak. South Post Oak is one block further west on San Felipe.
Neither of these two routes involve toll roads. If you do need to take a toll road, most of the tolls range from 50 cents to $1.75 with most trips around Beltway 8 passing a couple of these. There may be toll roads that you cannot access without an EZ Tag (Westpark, for example). If you accidentally get on one of these, you can call the toll authority and pay the toll over the phone.
Doesn't have to be, there are some excellent seafood restaurants all around the area, Kemah boardwalk is the most popular (used to be a very salty town, now more upscale). NASA is right there, they just brought the shuttle transport in, should be worth a look. Decent night life if you're into that. The weather this weekend has been absolutely perfect, humidity low enough to give you a static shock getting out of your car, 80's, clear, unlimited visibility. Hopefully it'll hold out for your visit.
You're the second person I've seen say this... Do you REALLY think it makes that much difference?
From the terminal, I'd probably take Will Clayton. But, from the rental car center? JFK south is pretty easy.. they have a flyover left exit right onto Beltway 8 east... traffic is rarely that bad in that area.
You have to go north (wrong way) to Will Clayton. I don't see how it saves any time??