First of all, I recommend the Rough Guide to DR/Haiti, by Sean Harvey instead of the LonelyPlanets. The book is notably more helpful on some matters and has lots of interesting background.
I dont think Bayahibe is comparable to Cabarete, but maybe if you head toward Boca De Yuma,w hich is a nice area. Bayahibe, so far as I know, is still pretty much just AIs, while Cabarete gives you a range of options. I stayed at Club Dominicus a few years back and I liked it just fine, but still it is an AI, and while I was free to walk up and down the coastline, there wasnt much else right there besides the resort. You can head to La Romana, Altos de Chavon, and other such places, but they are not within walking distance by any means.
Dont get me wrong, I enjoyed my stay there and I liked the beach, but in terms of ambience and the setup, the area around bayahibe seems very different from Cabarete.
You might try going to Las Salinas and the beaches just south of Azua. That part of the southern coast has very few tourists, and I think it is really nice.