goofy4tink,
I think (correct me if i'm thinking wrongly) that the Alamo on-resort is under less pressure to rent, and has a much lower rental 'turnover' - that is they are much quieter, and likely not expected to sell extra insurance as much. No doubt, they would happily sell you it if you asked!
The Alamo at International Airport is notorious for pushing extra insurance for no reason - likely a combination of staff incentives and high expectations from the parent company. They get rude when you decline and some use underhanded tactics like 'accidentally' printing off the agreement with insurance added, hoping you'll just sign without looking....