I am not from Colorado, but can tell you that having a Dr. pre-sign Rx's for you is illegal in every state. If you have read literature on this lately, I am sure you have heard about the NP in Florida whose M.D. left the practice leaving a pre-signed Rx pad. The NP wrote out Rx's with his signature, not knowing the rules ( and also being a new graduate such as yourself) and when the MD returned he pressed charges against her. She has been in litigation with this for >1 year, and is looking at doing prison time.
If you are required to do 1800 hours before having solo prescriptive authority in Colorado, I would suggest you keep track of your hours and make sure that you work in one office to complete the hours. If you now have MD's readily available to you to sign your Rx's I would play it safe and get the hours completed prior to moving on to an Urgent Care. If you want to keep track of your scripts as you mentioned above, keep a log in an Excel spreadsheet. This will ensure that you meet state requirments if you are audited, and you can keep track easily. This will protect YOU and your LICENSE! When in doubt, call the board of nursing.
I am sure that this has put a damper on your excitement to run out and practice, but states have laws and regulations for a reason. They are to protect YOU and the patient. I hope this helps.
Ashley C. Malick, ARNP, RN-BC