State Specific Question About: COLORADO (CO)

I just I read the postings under September 27, Jane's story, under the category, "Early termination process."

Oh, no...did I mess up? I rented in June on a 1-year lease to boyfriend + girlfriend; bf would be paying the rent. Found out gf moved out some time ago (no notice or date given). Had some conflict w/Oct. rent--check bounced; he paid with good funds, plus late fee, on the 15th and pd. Nov. 1 rent w/good funds. He also mailed notice that THEY are vacating on or before Dec. 1. (Lease is until June 21.)

I mailed an "Agreement to Cancel Lease" to my tenants and I SIGNED IT, asking them to sign if they agree and return it to me. The advice given to Jane, however, was to NOT sign a cancel agreement until the property is cleaned, vacated, and inspected.

My agreement has terms regarding payments, condition and key return, etc. The last statement says, " In the event that the resident does not fulfill the terms above or is in default under any terms of the Rental Agreement, the lease entered into is not cancelled and Resident is obligated to pay rent as agreed."

Will that cover me for having signed it before they did, or if they never do sign it? BF's notice to vacate says that all communication must be in writing. That's why I signed it and mailed it: can't carry it over or talk to him about it and I probably won't even be able to get GF's signature.