The prices on land are not going to go down because people know the economy will come back in a couple of years and so will the price. People are also hedging their bets that the "urban sprawl" of Houston will get out their way and make their land worth allot more.
Which brings something to seriously consider, what MIGHT move in next to you. I have several family members who lived outside Houston on 10+ aces with no problems from the busy bodies and no regulations. But the "urban sprawl" moving out around them and started trying to impose "city life" type rules on them. Even though the legally couldn't the developers and wealthy home owns started assaulting them with several lawsuits that cost the ten of thousands of dollars to defend eating up their retirement very quick.
Anywhere with in a 100 miles of Houston is going to be dealing with that type of warfare in the not too distant future.