8 weight is fine for most beach situations. Cabo is rough, but the further north you go, starting as little as 15 miles on the sea of cortez, the easier things are. On the pacific side, it's always a crap shoot. 9 is good for the beach and a good light rod for inshore. 10 would be better as first choice in the boat for everything but the brutes, 40+ pound dorado, yellowfin, you get idea.
If you were going to build one rod I would definitely recommend a 10 wt. based on what you said you were going after. If sails and tuna are on the agenda, I would bump that up to an 11, and the 11 would still let you fully enjoy the smaller game.
If you want a good deal on a redington 10 wt, DFR instead of building give me a shout. Remember, redington is lifetime warranty for the rod, not the owner. Call first to make sure things haven't changed and they are still supporting the DFR since Sage Purchased them