I live 35 minutes north of Providence and have ridden RI, CT, and MA extensively. I would suggest taking RT 1 South from the Airport, right on RT113 (becomes Wakefield St) to RT115 North in West Warwick to Fiskeville (becomes Main then Seven Mile Rd). Take a left on RT12 West and ride RT12 to RT102 (left) then right on RT94 to Foster Center. Continue across RT6 (very busy) and make a left on E. Killingly Rd. In East Killingly pickup RT101 and head west through Dayville, CT. About 5 miles outside Dayville, turn right on RT169 and follow this road into Woodstock, CT. Riding through Woodstock you will hit RT197. Turn left and now you are on the Adventure Cycling Atlantic Coast Route on Section 1, MAP 13.
Camping is sparse in this part of the country. There are some private campgrounds but few and far between. You might ask locals in Woodstock, CT for some suggestions. After leaving West Warwick, RI, dont plan on seeing any motels until you get to Dayville, CT. (or possibly Danielson, CT which is 4 miles south of Dayville. After leaving Dayville, then the next reasonable place to motel is Windsor Locks.
You will be urban until you get to the North and West of West Warwick, RI (which will not take very long). Then you will be among some of the most beautiful rural parts of Rhode Island and Eastern Connecticut. There will be many miles between services when you are not near an interstate highway. Traffic will be heavy around the airport and West Warwick, but smooth sailing afterward. Roads are in exceptional condition most of the time.
You will be riding some of the hilliest country in southern New England. The grades are steep 6-9%, but typically short (<1/2 mile) in length. I road cross country last year and used these hills for training (which they were ideal). There will be plateaus and deep valleys, lots of ponds and lakes, and many miles of the rollers I referred to earlier. You will enjoy this area.
If you have specific questions, would like a cue sheet for the area I spoken about, or maybe a riding companion for a part of this leg, then email me at firstname.lastname@example.org
Have a great trip.