Yoko is probably the most pragmatic of the Gurren Brigade, and while she has the knowledge to pilot a mech, she much prefers to shoot things with her gun. Prefers, as in, opens the cockpit of her mech in mid-flight so she can shoot out of it.
The series is complete, but I'm not sure of the DVD's can be purchased in the USA or not. Check out the Gurren Lagann thread for more info.