Here's you a start regarding what's hot and what is not: Cabo Fishing Report and Forecast - Seasonal Fish Chart - Cabo Fishing Tournaments Unfortunately it is not a great time for fishing and why the Black & Blue is held in October there. Even though they note that Striped Marlin are still active, IMO that's just more of an enticement thing. Their chart may/may not be on for Yellowtail in that April seems to peek for Loreto up the coast, and though some folks here I believe have stated they hit them on the fly, I've never done it.
As to guides, I'm not even sure if the guys I used to know are even still in the area it has been so long for me. Do a little googling though, look for the IGFA logos at sites and so on and whatever you do... Take lots, and lots, and lots of money if you'll be spending your time in town, and not at an all inclusive.
These guys are definitely worth a try. Welcome Looks like their web site hasn't been updated in awhile, but if Grant is still around he's worth fishing with. The tri-hull boats have a nice stable casting platform perfect for fly fishing.