There are several organizations, and even tour companies, around that offer this type of hands-on tour. Some are for the more experienced, but quite a few are available for beginners and families. If it is a beginner tour, you usually spend the first part of your trip learning how to dig correctly. The best thing to do is to decide where you want to travel or a historical area you wish to explore and then look up what digs are taking place in that location. Many of the tours are in the summer months, but a few are year round.
Maya Research Program