http://www.theflightdeal.com/2016/08/16/american-286-san-francisco-washington-d-c-cleveland-cancun-mexico-roundtrip-including-all-taxes/
날짜는 holiday 빼면 완전 wide open이고요,
ITA Matrix나 간단하게 google flights로 찾으면 되네요.
친구들이랑 같이 갈까 생각중이에요.ㅋㅋㅋㅋ