OH HECK NO!!! They may be legitimate - but they will buy your home for rock bottom price and you will get the short end of the stick.
Find a real estate agent - use Angie's List - better business bureau and find a reputable agent.
Make your home ready to sell in order to get the most money for it.
make sure your finances are in order and your credit report is good to go for a new mortgage - you don't want to be caught off guard if your home sells quick and you can't buy a new place!!
Before you sell - find an inspector and have them come and inspect the home to see what needs to be done BEFORE you sell - this will make things much easier when you do get a contract on the house and they have their own home inspection - you don't have to worry about what they will find or say needs to be replaced, etc.
Have an old roof? Expect potential buyers to want credit to replace it.
Same with heater/AC - especially in Texas!! :)
Clear out the clutter. Yes, I know - but really - it will sell faster if people don't have to walk around toys - and can see themselves there.
Have open houses - PLENTY of signage and advertising!!!