First, I agree with gbopp about waiting due to training the dog. You don't want to get a dog familiar with RV life/travel during a big trip. That's a lot of added pressure, and if the dog doesn't handle it well, it puts you in a tough spot. Better to get the dog used to RV life/travel during short trips that you can plan for dog-friendly places and activities. Also, you don't want to have to deal with training issues like potty training, obedience, etc. on the road in unfamiliar places.
As for having a dog while sightseeing, yes, it will affect things. Some places don't allow dogs - on the trails, at the sights, at the campground. That means, you will have to leave the dog in the RV alone (which may be against campground policy) or get daycare for it. Daycare will increase costs. In addition, you will be less likely to change plans on the spur of the moment - that great restaurant you heard about from another tourist sounds great tonight, but we've got to get back and let the dog out to potty OR we have to pick up the dog from daycare or will be charged late fees.
I love dogs and I have dogs. But taking them on the road does change how you do things. If you've already got your trip planned out, then wait on the dog til you get back. Otherwise, you'll be spending your time reworking plans because those places that interest you won't let your dog in, etc.
As someone who has done pet adoptions, I'll also add that when you get a new dog, you want to be able to provide a consistency over the first few weeks, letting the dog get accustomed to his/her new home and people, before you start mixing things up. Jumping into a big trip during that time could increase neurotic tendencies in a dog that already may have issues.
If you had the dog for a while AND the dog was familiar with RV life, then I'd say go for it knowing you may have to board, etc. at times. But with a new dog, I say wait. It's undue stress for both you and the dog otherwise.
If you have a dog in mind, talk to the breeder/foster/shelter and see if they can work with you. If not, then just wait until you get home and then commit time to the dog. Then you can take small trips, getting the dog used to the RV, camping, sightseeing, etc. and build from there.
1975 American Clipper RV with Dodge 360 (photo in profile)
1998 American Clipper Fold n Roll Folding Trailer
Both born in Morgan Hill, CA to Irv Perch (Daddy of the Aristocrat trailers)