One of the main ingredients that makes CrossFit so special is the universal scalability of every movement. Are you a terrific runner? That's awesome, you can run with a vest, or a sled, or row or bike... Can't do hspu, so you avoid hspu days? We have tons of scales for those to help you improve- but if you just avoid them, they'll never get better.
Greg Glassman has said that CrossFit works to prepare you for "the unknown and the unknowable." There will be some tough wods. There will be some distance running. There will be strength only days. There will be DU, and MU, and sprints, and abs, maybe some Jane Fonda, definitely some tabata. Be prepared every day- bring your running shoes, bring your jump rope, wrist wraps, whatever you might need. A lot of you will surprise yourselves by taking on things you didn't think were possible.