“I believe he himself has said it would be a wall from El Paso to San Diego. Someone correct me if Im wrong.”
Only place this is feasible, there will never be a wall on the Texas border.
According to Google Maps, riding a bicycle (most proximate route along the border) from Brownsville to San Diego is 1,566 miles. The route of course bypasses Big Bend at the Rio Grande and the southern border of Arizona. Add those in and I'm betting it's around 1,989 miles. So yes, a 1,989 mile long wall will include the Texas border. Here's the route:
San Diego to Brownsville