I would probably rely on liquid carb intake (e.g. Gatorade) during a half because generally they digest better IF I could trust a) the person mixing it or b) the person handing it to me. Neither of which I generally can. So I usually carry a gel. I suggest that if think you will be out there for longer than 1:50, you carry two and less than that, just take one. Unless you are training for a longer distance triathlon or marathon and want to practice, you may want to try and take an extra.
Make sure you take a good two cups of water to wash those gels down. And plan ahead so you're not surprised by the aid station, you have your gel out, open and ready to eat.
Let's take this example of the Santa Cruz Half Marathon to plan a nutrition strategy in advance. Click here for the course map where the aid stations are marked with a bottle.
So for slower than a 1:50 goal time I would take a gel at 5.5 miles (Station 3) and 9.5 miles (Station 5).
For less than 1:50 goal time I would take a gel at 8 miles (Station 4).
Just a little bit of planning can take the stress out of nutrition and allow you to focus on the race and your running.