| Cheap Flights: Austin to/from San Juan $140-$165 r/t â Spirit Spirit has round-trip flights from Austin (AUS) to San Juan (SJU) for $140-$165 with a connection. Flights February to May. Note: Spirit fares do not include a free carry-on bag. Only a small personal item, like a Jansport City Scout backpack is free. You can avoid paying for seat selection if you accept the randomly assigned seat prior to boarding. Note: Spirit seats only have 28-inches of pitch; 2-to-3 inches less space than most other airlines. We donât charge a subscription fee. All of our deal notifications are available for FREE via Instagram, Facebook, Twitter, our Webpage, and our E-mail list. If you are paying someone a subscription fee for our content, you are being ripped off. Read More Cheap Flights: Austin to/from San Juan $140-$165 r/t â Spirit . | 