Bro, Availability depends on your need , What kind of night life you looking for ? Just to hang out and 1,2 beer ?? go to any bar in thamel and its good. Want to see what top quality bar is like- go to ROX or yak n yeti. If you're thinking about sex , go to nude bars in sahid gate or thamel (dont tell me that having been to strip club, you dont intent to do so in kathmandu believe me the feeling you'll have is amazing... may be aafno bhaneko aafnai ho.. nepali KT haru), if looking for really cheap stuff, go to Cabin restaurent.