TACS is open to anyone at any level who is interested in computer science. Although most of its activities are geared toward computer science and electrical engineering students, anyone interested in the field is welcome to participate. Although we do not require membership to attend meetings, we do ask that you join on a local level if you are a regular participant in TACS activities. Your dues go directly back into the organization, so your money only goes to make it a better experience for you. With your local membership, you are guaranteed first priority in all events that TACS sponsors.
Most people join either one or the other, and the choice is generally just personal preference.
If you participate and WIN the local programming contest in the fall, you will be asked to join ACM in order to participate in regional competition. Go here to fill out the online application.