I haven't been there myself, but I have heard that "Stamp Diego" is a good place to go (and they carry A Muse!). If you go to the A Muse website, click on "retail locations" to find other stores in the area that carry their stamps. You might want to call ahead though to make sure they still have some in their inventory.
http://www.amuseartstamps.com/
Also, there is a scrapbook store in Carlsbad called "Ever After" that I visited in November when I was down that way. Big store, lots of paper and ribbon. I don't recall any Marvy punches. They had a few stamps (no A Muse). Hope this helps! Have a GREAT time!!!!