If you signed w/ an NCAA school and want to attend a JUCO or NAIA school and you have not attended a class at the NCAA school yet , you can go to the JUCO or NAIA school and run XC immediately. I would first ask for the release as it is the correct thing to do. But, you will not need a release to attend the JUCO or NAIA school. They are governed by different bodies.
It is bad for the NCAA school as they have no time to find a replacement for you. So, if you can stick it out one year a the NCAA school, that maybe best. Then you could ask for your release to another NCAA school or just leave and go to the JUCO or NAIA school and then you have fulfilled your promise as scholarships are one year deals.
Do not feel too bad for the coach, unless he/she has been at the school 25+ years, they would probably leave your school today if a PAC 12, Big 12 school came calling for a HC.