If you want a really good rate at the Andaz WS, you could also instead do a best rate guarantee for Friday and Saturday night only using Kayak.com. Kayak is showing $293 vs. Hyatt $325 per night, so that'll get you down in the $230s per night! Similarly the third night is $428 on kayak vs $445 on hyatt.com, so that would get you down in the mid $300s.

Personally if it was me, I'd do the Andaz WS with the best rate guarantee for the first two nights, then swap to 48Lex using points for the 3rd night (if you don't mind swapping hotels mid way). That way it would only cost you mid $400s cash total plus 15,000 points and you get to try both.

In general though, unless I need the stays/nights for Diamond status, my personal rule of thumb is to try to redeem points for about a $0.02 redemption rate to be worth using points.