Personally, I'd take it back to Mike's Bikes and complain. The reason that spokes would continue to break would likely be that the guy who replaced the spoke didn't properly tension the spokes. Mike's Bikes isn't the best for vintage bikes but they should at least know how to properly true and tension a wheel.
A much better bike shop for vintage stuff is Missing Link, literally 1 block from Mike's. The closest bike coop that would have used wheels is Waterside Workshops which is down at Aquatic Park near the freeway.