For trading through Interval into Cabo San Lucas, Casa Dorada on Medano Beach would be a very good choice, right in the center of the action on busy Medano Beach. You can walk to lots of great restaurants and beach bars from there. It is not a mandatory all-inclusive resort.
Villa del Palmar and Villa del Arco are farther down Medano Beach from town, but both are very nice resorts. V. Del Arco is more upscale, but double-check all-inclusive requirements. I've seen some VDA units require A-I, some didn't.
For a quieter lux experience, I'd choose Grand Solmar at Land's End. The studios are quite large (700+sf), with a separate BR, dining area, big balcony overlooking the Pacific Ocean, and decent kitchen (no oven). The 1-4BR's are fantastic - if you can get one! Solmar Beach and Land's End are stunningly beautiful, and an easy walk to the marina and downtown for shopping/restaurants. It's not a mandatory A-I resort.
Fall is great for sport fishing in Cabo, and the multi-million dollar Bisbee fishing tournaments are held in October - it's a fun time to be down there!