For total beginners we recommend December to March, since the waves are small then (2 to 4 feet) and the weather is hot. But, please note that Brazilian summer holidays extend from Christmas until two weeks after Carnival, with many Brazilian tourists around (especially surfers...), and much higher lodging prices than during  the low season. From April to September, temperature drops and from June on waves get bigger, between 3 and 7 feet (up to 10 feet in July/August). On the other hand beaches and peaks are crowd-free then.