Absolutely! You can even do IAD-SAN, a week later SAN-HNL, a week later HNL-IAD for one award price (40,000 miles at Saver Econ to visit two cities)! But seeing that you're from near the SAN area you may not want to go back to IAD. =)

But know that UA lets you have 1 stopover and 2 open jaws for ONE award ticket if you want to maximize it all.