Mostly yes. But there were also arrests and prison/deportations for "subversive activities" i.e. possession and distribution of communist literature.
The only person sent to prison for being a member of the Comunist party was Junius Scales of North Carolina. Arrested in 1954, after two trials and many appeals he was sentenced to 6 years.
In 1962 President Kennedy commuted his sentence to time served.
The Supreme Court later ruled the law that was used against Scales, "Smith Act", was unconstitutional.