Suits certainly are not required, since this is an informal, social event that focuses more on conversation and information exchange.
Jeans are acceptable.
There is no pre-event registration for students. Note, PTC companies will receive a packet with event details once their registration forms are processed. Students can contact their respective colleges to see what sort of transportation is available. The same companies will be present for the duration of the event, and there is no schedule that must be maintained. You can discuss internship or career opportunities, or just listen as they demonstrate their technology.