We tip a minimum of 20% and usually more since we tip on the total check, not the pre-tax amount. Where the gratuity is added automatically it's invariably 18% and it's always pre-tax.
In places like the Orlando Ale House, we usually end up tipping 30% - 40%. When you can get 4 beers and 2 lunch-time entrees for less than $25, plus a great hour or more chatting to the bartender

, it just seems wrong to leave $5.
As far as DDP goes - there's absolutely no need to leave an additional tip, albeit from January the tip will NOT be included.
We tip 20% on bar tabs, too. Some tip $1 per drink. If you pay attention, you'll discover that many Americans tip less.
The valet/bell-hop issue is a big bug-bear of mine and one I've mentioned several times before. They seem to have a finely-honed system worked out. You tip the guy who takes the car away. Then the guy who takes the bags from the boot (trunk

); yet another takes them to the room. If they store your luggage for you (even though you've tipped the guy who kindly arranged it), you can be sure that a different person will take them to the room. I really think that if you check in early (and tip appropriately) and then go off to the parks, it wouldn't be unreasonable to expect to have your bags delivered to your room whilst you're out. We really cottoned-on to this racket when we did a road trip back in 2005. We were checking in and out of hotels every couple of days and you go through this triple-tipping con every time you check in
and out. Boy does it get expensive!
We've just arrived home from Reunion in Orlando which is a cashless, tipless resort. I have absolutely
no problem with tipping whatsoever, but not having to think about it does make for an extremely relaxing, stress-free stay.