From the FAA’s Airplane Flying Handbook on approaching non-towered airports:
“One method of entry from the opposite side of the pattern is to announce your intentions and cross over midfield at least 500 feet above pattern altitude (normally 1,500 feet AGL.) However, if large or turbine aircraft operate at your airport, it is best to remain 2,000 feet AGL so you’re not in conflict with their traffic pattern.”
Note that when flying visual patterns at a non-towered airport you’re doing VFR, so you’re responsible for looking for other aircraft potentially in your way and avoiding them.