Rescued Cavaliers are the best. That said, if you're thinking of adopting, a few thoughts I might share.
The dogs who come into any rescue are typically of all ages, from youngsters through seniors, but most are adults. And those juveniles also normally have many adopters waiting, so if that's your hope, well, you may have to get in line. The likelihood of a senior being available in the short term are much higher.
Then, while some Cavaliers needing homes have special needs or ongoing medical concerns, most are healthy and their medical needs are taken care of while in any quality rescue. So families open to adopting a senior or special needs Cavalier may have a greater chance of finding a rescue since these dogs are often harder to place.
A good rescue always tries to make the best match possible between the rescue dog and the families looking to adopt. So also be prepared for an adoption process that is a thorough one.
But to my first point, Cavaliers are great . . . and rescues are the best. There's something about the bond that builds for being their forever home. They know, and you'll know a love like no other.