I-10 to I-8 is fine. Drive that route several times a year. On I-8 there is a border patrol checkpoint heading west in California but its quick and easy and most likely you won't even stop. In all the years I've not been stopped once nor seen anyone else.
Between Gila Bend and Yuma there are only a few places to get gas. We usually fill up in Gila Bend at the Pilot which has a McDonalds or Wendy's next door.
At Yuma there is a truck stop on Fortuna Rd. on the north side of I-8. At El Centro there is a truck stop off 4th street, south 1 block then turn right on Wake Ave. There is an RV park on Wake to the left of 4th st.
Before passing El Centro make sure you have plenty of gas. Between there and El Cajon area I'm not aware of many RV friendly gas stations except for the Golden Acorn Casino at I-8 mile marker 61.
As for being near the border in a few areas you won't notice it. No problems at all.