Short answer yes you have limits its set in the Acceptable Use Policy (AUP). Which you can read here »www.cableone.net/Pages/internetaup.aspx
the A La Carte package is the 5mbps plan so your limited to 3 Gigabytes a day tracked from 8am to midnight. Now are they enforcing that well that depends on where you live and how often you hit the cap. I've hit the cap 8 times in one month and no letter or warning so far, your results may differ. Now if you want to see how much bandwidth cableone shows you used just go to www.cableone.net then click My Services, My Account log in and click on My Bandwidth.