You can cancel/rebook at no charge. Be sure to check prices and look for new coupon codes. If you are a paid member here the Transportation thread always has good deals being shared...otherwise use Google. I rebooked mine twice which ultimately got me $50 off my original reservation....and thats typical. Unless there is some massive convention that week you should be able to get a standard car for about 175 or less (including all fees and taxes).
