I didn't go to Canoe U, but I raced against their lights pretty frequently in college. USNA is in the oldest and most competitive rowing league in the country, the EARC, and they have had some very fast crews recently. Where I rowed, our workout schedule would vary somewhat by the time of year- we would have practice at minimum one practice six days a week for the whole year, with 2x/day practices being pretty standard anytime at all close to a race. However, even when the extra practices weren't scheduled, it was expected that anyone who was serious about making a boat would take the initiative to show up and work out on their own, since that level of training was basically necessary to be physiologically competitive.
You will have practice through the entire academic year, including the whole winter which you will spend indoors on the rowing ergometers and in the "tanks." I'm not sure about the summer, since I seem to remember the EARC having a rule limiting the number of weeks that a team could spend on the water, plus I think that USNA mids are typically pretty busy over the summer with cruises and other stuff like that. I think the Chief knows more about USNA specifically, but other crews in that league have their summers off.
It is very true, as was said before, that you can easily row as a freshman without having any prior experience (I can't tell from your first post or your profile if this is the case). Most college crews will have a relatively even mix of rowers with high school experience and those without, and they will organize practices for the frosh/plebe team to get the novices up to speed over the first few months.
And yes, the Chief is right that rowing in sunny Annapolis is much more pleasant (at least in the winter and early spring) than rowing in Ithaca, Hanover, New Haven, or Cambridge. Breaking the ice to get back on the water is the fun part. The hard part was walking to practice, seeing the river frozen solid, and knowing how much more time we had to spend on the erg.
Hope this helps.