I don't know what US airlines you're flying but I consider AA one of the worst in the world in F.

Of course you can use the call button. That's what it's there for. Personally, I tend to ask as the crew pass but if I can't see them I use it.

I've never had a flight run out of food, in long haul F or shorter J sectors, such as CAI.

If you want to guarantee a choice, just tell the crew once you've sat down. If you want to dine on demand also tell them. The service on shorter, wide body routes is planned, however you should be able shift it.