If you are courageous enough to drive in São Paulo (it is not dangerous but it requires a lot of patience) you can hire a car at Guarulhos. There you can find several car rental companies including Avis, Budget, Hertz, Localiza and Unidas. Since you will drive to Ribeirão Preto it is advisable to hire a car with air-conditioning. The State of São Paulo boasts the best highways in Brazil and many of them are as good as their counterparts in Europe and North America. To drive in the State of São Paulo you should know that São Paulo highways are referred to by their names instead of by numerical codes. Every highway has a numerical code for sure but nobody uses it and even the official road signals refer to the highways by their names. So, to go from São Paulo to Ribeirão Preto you should take either Anhanguera (pronounced Anyangwerah) or Bandeirantes (pronounced Bahndeh eerantehs) highway. Just for completeness, the codes of the Anhanguera and Bandeirantes highways are SP 330 and SP 348, respectively.
After leaving the airport you should follow the directions to São Paulo and then to Marginal Tietê. Marginal Tietê is a beltway that goes along Tietê River crossing São Paulo from east to west. It is relatively easy to get to Marginal Tietê from Guarulhos and once there you should drive for about thirty minutes (if the traffic is flowing) until you see directions to access Bandeirantes highway. There will be a sign at the right-hand side indicating Bandeirantes Saída Exclusiva, which means exclusive exit to Bandeirantes, and you should take it. If you miss it you will have another opportunity to leave Marginal Tietê by taking the Anhanguera highway exit some kilometers ahead.
Whatever highway you take (it is preferable to take Bandeirantes), once you have taken it you are on your way to Ribeirão Preto. Both highways are private, which means they are tolled. There are eight tolls (pedágios in Brazilian Portuguese) between São Paulo and Ribeirão Preto.
Bandeirantes is a modern highway with three or four lanes each way and its speed limit is 120 km/h (74 mi/h). However, it does not go all the way to Ribeirão Preto because it merges with Anhanguera highway at km 173 (around a city called Cordeirópolis just after a Nestlé factory at the left-hand side of the road for those who are driving from São Paulo). Anhanguera is a somewhat older highway with two or three lanes each way. Its speed limit is 100 km/h (62 mi/h) until Bandeirantes merges with it and then it becomes 110 km/h (68 mi/h).
On your return ride you should leave Ribeirão Preto by Anhanguera and take Bandeirantes to reach São Paulo by the fastest route. When Bandeirantes arrives in São Paulo it bifurcates into two roads, one to the right and the other to the left. You should take the left one (the signs will indicate Marginal Tietê – Zonas Norte e Leste). Then you will be at Marginal Tietê and you should continue along it until you will see the indications to Guarulhos International Airport).
If you are a nature lover and wants to stretch your legs with a walk of about one hour in the middle of your drive to or from Ribeirão Preto there is an excellent option at the Vassununga State Park just beside Anhanguera highway at km 243 (74 km from Ribeirão Preto). You will find in this park one of the oldest living beings on Earth, a Jequitibá Rosa tree (Cariniana legalis) about 3,000 years old. The forrest patriarch as it is called is a magnificent tree about 40 m (131.2 ft) high with a 11.3 m (37 ft) circumference trunk.