You don't need to use twitter, you just need to know the twitter page of the truck you are following so you can find it.

Just bookmark that page, and click on it when you want to find the truck.

You don't even need a twitter account to do that in most cases (though some trucks may make their posts private, so they can collect you name, but I think that's the very small minority).

For example, if you were following one of the ice cream trucks in Manhattan, all you would need is this link

http://twitter.com/#!/VLAIC

It's to their twitter page.

Yelp is probably another good source, but if they move around and have chosen Twitter or Facebook or Google plus or whatever to be the way they release the information, you won't have much luck finding them any other way.

It is also possible there's somebody who groups all the different postings into one place, but in most cases they will use twitter to relay that information. Again in New York, here's a page of somebody or some group who does dozens of food trucks

http://twitter.com/#!/MobileCravings/ny-food-trucks

In a strange city I would just google

<<name of city>> gourmet food trucks

and there will probably be links to dozens of reviews in magazines and papers about the rise in food trucks in <<name of city>>