I was recently scammed at the Mega in San Jose. I used a 100-peso note for a 49-peso purchase. The clerk rang it up as a 50 and handed me one peso in change. Since I was certain I had only new bills straight from the ATM I knew I had nothing smaller than a 100; so I called her on it. Other customers (Mexicans) tried to help me, but to no avail. She stonewalled and refused to check in her drawer. It wasn’t worth fighting over $5 so I left. But I am now forewarned, and so are you.
What to buy: Just be careful
What to pay: Exact change if you have it
Yes Cabo has a Costco and its just like in the states. When we come to Cabo with the kids we usually eat in the condo. This saves us alot of money because the food can get expensive in Cabo. so we usually bring some things from home since the flight is so short or we will go to Coscto.