Hi Olivia,
I am nearly 27, have been hearing impaired since birth, and have gone on 2 RS tours--first solo and second with my dad.
While I agree that traveling can sometimes be a challenge, it's certainly no reason not to go. Both of Rick's tour guides were extremely accommodating and helpful about my hearing issues and that's an excellent way to go if a tour interests you.
The biggest issue I ran into was when they used headsets which was in the Vatican Museum on the first tour, and throughout on the second. However, I figured out the second time that if your hearing aids have t-coils (for the telephone), look into getting a Music Link. It plugs directly into the headphone jack and feeds the sound into your hearing aid's t-coil. The only downside is you won't be able to hear people who aren't speaking into the microphone unless you switch back off the t-coil.
If that's not an option for you, try staying closer to the guide. With the smaller group sizes, I found it was fairly easy to stay within earshot and if I missed something, my fellow tour members were only too happy to help fill me in.