Absolutely! As long as you are flying on a participating airline, and you are completely done with checking in no less than 3 hrs prior to flight departure, you're good to go.
The RAC counter opens at 5am, and it takes about 15 mins to get checked in, not including any line wait times. That means that if you have a flight before 8:15am, you probably can't use RAC. I even say that any flight times prior to 8:30 are iffy.