There isn't much 'guiding' that can be done at a giant food fight. The guide takes you there, you throw tomatoes at everyone, the guide takes you back. Because of this, each of these tours offers more than just transport to and from the tour, with tours of other sights in the area.
If all you want is someone to guarantee you get to the fight on time, I recommend the first tour, which is the only one that lasts a single day (and so is the cheapest).
1. Tomatina Tour: One Day
2. Three-, Four- or Five-Day Tomatina ToursFrom Busabout, the king of Antipodean-dominated bus tours in Europe. Most of your follow travelers will likely be students between 18 and 25.
You have a number of choices from Busabout, depending on how long a tour you want and the type of accommodation you need: