Torn ACL-friendly activity?

I've been out for the season with a nearly severed ACL since early December. I'm a 21 yr old active college student, and not being able to ski is killing me. Doc said I could do some light-duty skiing with my brace, but I know i wont be able to just cruise greens all day, so i decided to stay off the slopes so I dont further injure myself. Surgery is slated for May or June once school's out. I've found a decent amount of enjoyment in ice skating at the local rink... it's cold, and has similar motion to making turns on the slope, but gets boring to me after about 45 minutes. Spring is coming, and I'm also a pretty avid mountain biker, but am not sure if that's something that I should venture into with a torn ACL... I haven't found much info on this subject, and am looking for personal experiences/opinions, and suggestions as to what else I can do to get outside and stay physical other than just jogging. Thanks in advance...