If coming from Bayahibe by publico, you'll ride across the bridge spanning the Rio Salado onto the bustling 4-lane Ave. Libertad. You'll need to immediately visually locate the long, narrow parking lot-type passageway which runs parallel to the left/south of here. It's where the publicos wait for departing back to Bayahibe. A one-way ride either way is 20-pesos.
The publicos make several stops into town, though I suggest staying on until it arrives at Parque Central which is the focal point of the city. The Codetel office is located on the eastern side of the square as are three smaller bank branches which can serve you without the wait...unlike always crowded Banco Popular which is located south on the street on which you'll enter the square.
For transportation transfers on to larger regional gua-guas and private lines, the station for buses headed to Higuey and San Rafael de Yuma/Boca de Yuma is on the street heading north out of the center and located across from the east side of the church. Buses heading west for San Pedro de Macoris, Juan Dolio, Boca Chica and Santo Domingo depart from a station off the northwest intersection of the square.
If you need to purchase anything not found in the local colmado, there are two megastores equivalent to our Wal Mart Supercenters. Directly behind the church is the open-air city market and one block north of there is a tall pastel-orange building which contains ORENSES Department Store. An even larger selection can be found at IBERIA - a pleasant walk through the city two blocks west from Orenses and then three blocks left/north along Calle Francisco Ducoudrey. Both stores readily accept major credit cards. Be advised they check all bags...and while I never had anything missing, you might consider leaving any valuables that won't fit into pockets back at your hotel and to carry your camera.
One block north of Iberia where the street is the large public hospital center, though unless dire emergency, you'd be wise to seek out a private physician.
If not walking, taxis are everywhere; motorconchos even more abundant. Anywhere on a motoconcho in the city cost RD10 when with local friends, RD20 when a tourist by myself. Might I suggest for motoconchos you at least wait until you can flag down an older, more experienced driver to minimize risk.
*For maps, Lonely Planet's DR Guidebook has about the most detailed one for the city.