I made my reservations last fall after attending ACL for the first time. Definitely stay in town if at all possible. I really don't worry about headliners. Just look back at the previous years. The lineups were great, even if you don't like the headliners. Besides, the aftershows are great too.
I'd definitely suggest ACL - be prepared for heat as already mentioned - but it's a bit later this year. Here's hoping it helps.