Fun City and Good Food for a Few Days
I really enjoyed Siem Reap, and realized it even more so after visiting dirty Phnom Penh. The Pub Street and Market areas have a really fun and enjoyable vibe. There's something for everyone. I'm 24 but not much of a partier, and I had a blast sampling the different happy hour cocktail specials along the street. Food is delicious and cheap if you look in the right places. I did the Angkor Wat 1 day pass for $20, which for me was perfect. I saw ~11 temples; that's more than enough!
Insider Tip:If you'd like to get out of the town, take the Tara River Boat trip to see the floating village on Tonle Sap lake. It is not touristy or gimmicky at all, and I had a great time with a wonderful guide. I did the half day trip, which was an excellent option when it's so hot outside.