Stayed at Mission RV right in El Paso on I-10. Not the greatest park but it will fit your 5er in a pull thru and great location to see El Paso. Just dirt (no grass) marginally clean and fairly safe. Pull thrus are very close but they try to leave every second space open if they can. Downside for us was that tent campers are put in pull thru sites. It can be noisy...it was for us as we had tent campers on both sides of us.

If you can stay in Las Cruces, NM, instead there are a couple good campgrounds on Passport America and others like Hacienda, that are really nice. Las Cruces is also viewed as a safer area than El Paso.