Boa Vista is a city in Brazil.
South towards Manaus
From the bus terminal if you walk west up Avenida das Guyanas to the large roundabout, then make a left down Avenida do Brazil and walk a little down south on Av. Brazil you will reach a petrol station on the right, just on the corner of Centenario. From that petrol station a lot of truckers head out to Manaus, it may take a few days and a lot of conversation but you should be able to find a lift sooner of later. The people in the restaurant are very kind and will help you out with hot and cold water and anything else they can if you just ask. You can also hang out on the tables and chairs there if you like, they don't seem to mind.
Accommodation and Sleep
Just over and a few hundred yards down Centenario from the petrol station, there is a patch of tall grass behind a bunch of mango trees. In the far corner of the grass you are invisible from the street and it's fine to pitch the tent. Oh and check out the mango trees they can be very generous and it doesn't seem like anyone picks these ones! If you are the more urban kind of camper, the people in the gas station restaurant also let you sleep there if you ask. They close the restaurant at about 21:00 and then it's all yours.