We are both retired military and use Express Scripts Mail Order for our medications. I can't speak to your 30 days supply meds, but we use the Express Scripts website to input a temporary address when we need to refill meds. Then order the refills. Sometimes if we are comfortable with the campground where we are going, we will order in advance of arriving and call the campground to let them know to watch for our package. We have not had a problem now that we can input the temporary address and the effective dates ourselves on the website. We did have a couple hiccups before they updated the website when we had to give someone the temporary address over the phone.
We have also been able to call and ask for an early refill once or twice when our travel plans were going to make being in one place a little difficult.
Good luck.