Mix it up. Go with variety.For those of us that are going to be living the tour vicariously through youtube and (hopefully) a live DVD somewhere down the line, doing a bunch of different songs makes more sense than doing the exact same set list every night.
I hope they mix it up. If they do both an LA and San Diego show, then I'll go see both, and would love to see different songs each time.
Personally I think that mixing it up wouldn't be so great - I think they'll sound much tighter if they have at least 3/4 of the setlist as a constant, maybe shifting the order of the songs each show.if they play 24 songs a night, then I think 15-17 should be constant and then the last 7 or so can go with the flow of the night (what the band feels like playing and what the audience asks for).
Kind of like Helmet nowadays, keeping the "obvious" ones in and throw in a LOT of variety. Also try to take in requests, that´s the coolest thing they can do for their fans.
MIX IT UP. As Kevin mentioned above, if this does turn into a stateside tour, then I'd love to see multiple CA shows, hoping for a different setlist each time.