Ah Yes, the ride to the Keys!
Where are you coming from? Where do you want to stay?
Best advice I can give is if you want to stay in Key West to take in the sights & experiences there, is to stay on KW. Riding down from another Key & trying to park can sometimes be a hassle. When you book your lodging be sure the place has ON SITE parking. Otherwise you will have to park you bike {or bikes} on the street at night. Not something I would want to do! If you can get a place within walking distance of the Duval St. hot spot all the better. Bicycle & scooter rentals abound if you get further away. Just get there & park the Valks until you are ready to tour other islands or leave.
As far as the trip down you can make great time on the Turnpike, I95, US 27, or I75 to the Alligator Alley. But once you get to US1 in Homestead or Florida City it will be a significantly slower pace. Same through most of the Keys. As usual anywhere in Florida, watch out for the northern tourists & other non-English speaking drivers.... they will pull right out in front of you!
It is a GREAT ride through the Keys as there is no where else like it anywhere. We stayed on Marathon twice in the last couple of years as we were interested in other islands too. Marathon is dead smack in the middle of the Keys.
If you are interested in diving/snorkeling there are PLENTY of places that can take you out to the reefs & supply you with all gear so no need to tote your own.
On KW, I enjoyed Mel Fishers place, Hemingway House, & anything to do with the history of the Keys. Kim liked the shops & bars.
I've been there dozens of times lobstering over the years but only twice on bikes. Take your time touring around & you will have the time of your life!
In front of Mel Fishers Museum on the Rocket 3.
Obligitory "Southermost" pic.
Same on Valk the year before.
Stop & see beautiful Bahia Honda SP. Just a bit after the 7 mile Atlantic side.

Larry the Lobster. He went missing for a while but I heard he's back some where!
Wife rode her 750 Spirit all the way down. Marathon.

Bud 'n Mary's on Islamorada.

One of the bst rides we've ever had!
Enjoy your trip!