Generally you shouldn't have a problem spending $100's but you may have some difficulties in taxis, convenience stores, tolls, petrol stations, etc. Don't use $100's for smallish transactions since stores will hate giving that much change. Also, be ready for some grimaces of annoyance from those who willa ccept the bills. Most places will use a special pen to check that they are indeed real $100's.
I'd take some $20s as well