Yes good chance its the thermostat but check for the electric fans coming on too,check the fan relay fuse etc..if it gets hot and you turn on the a/c the fans should go on and might bring the temp down if the fans arent coming on when you run it in the driveway and its at operating temp or higher then its a fan problem, some vehicles actually have a module that controls the fan operations, you should be able to zero in your problem running it up to temp and looking under the hood and watching if your fans come on or not.if the fans dont come on,turn on the a/c, if the fan goes on and temp goes down, its definetly a fan problem,If the fans are on and you have plenty of fluid, not too much antifreeze, not more than 50 percent mix for most states,and you still overheat most likely the thermostat,less likely its a plugeed radiator but not out of the question,so good luck to you and hope this helps...