(Adds details of protests, police response, weather)
By Brad Haynes
SAO PAULO, June 13 (Reuters) - World Cup fever gathered steam across Brazil on Friday as fans streamed to a second day of matches and violent protests subsided, although a last-minute scramble to get some host cities ready kept organizers on edge.
Brazil's opening victory over Croatia unleashed celebrations late into Thursday night, with fireworks and car horns echoing for hours in major cities as fans got into the spirit of the first World Cup on Brazilian soil since 1950.
Shopkeepers in Rio de Janeiro and Belo Horizonte on Friday cleaned up storefronts that they had boarded up for opening day, when protests against the costs and alleged corruption behind the tournament broke into scattered clashes with police.
Most of Brazil's 12 host cities saw anti-World Cup demonstrations ahead of the opener, drawing anywhere from dozens to more than 1,000 protesters, but the protests dropped off sharply early on Friday.
About 100,000 police are patrolling host cities during the monthlong tournament. On Thursday, police responded with teargas, stun grenades and rubber bullets against demonstrations in some cities.
Amnesty International said police deserved a "yellow card" after they "brutally repressed peaceful protesters" in Sao Paulo on Thursday. Protest organizers in some cities are pledging marches later on Friday and over the weekend.
Brazilians are still frustrated about the $11 billion spent to host the Cup in a country with glaring inequalities that struggles to fund schools, hospitals and other basic services.
President Dilma Rousseff was subjected to jeers and derisive chants at Brazil's opening game, a clear sign of the continued frustration. But many fans also want protesters to let them enjoy the party.
"They won't stop us having our fun, especially when Brazil win!" said Pedro Ribeiro, 29, a businessman in Belo Horizonte who held a house party until the early hours to celebrate the 3-1 victory over Croatia.
"People have a right to complain. There are lots of problems in Brazil. But they don't have the right to be violent or to spoil the World Cup we've all been waiting so long for," Ribeiro said. "This party is only just beginning."
The first full-capacity game at Sao Paulo's new World Cup venue went smoothly on Thursday except for minor hiccups. A partial outage of stadium floodlights and the late arrival of food at vending stalls did little to dampen the atmosphere.
But questions still hung over the other cities hosting their first games on Friday.
In the northeastern city of Natal, pouring rain, striking bus drivers and lingering safety questions about the stadium marked the run-up to the Mexico vs Cameroon match.
Temporary new bleachers only cleared 90 percent of a safety check on Wednesday, officials told Reuters, and inspectors were barred from entering the stadium on Friday while world soccer body FIFA prepared for the match.
As many as 100 fans were moved to alternative seating due to safety concerns about the new bleachers, a FIFA spokesman said. Mexico won the game 1-0.
Natal also resorted to using school buses and vans to keep public transportation flowing after a bus drivers' union voted to strike over a wage dispute.
Making it more difficult, days of sunshine in Natal gave way to driving rain that flooded city streets and drenched fans in the Dunas arena. The downpour knocked out some of the stadium's security scanners.
Rain in Porto Alegre also interrupted construction around the World Cup arena, which remains a muddy work site just two days before hosting France vs Honduras.
In Cuiaba, a dry heat cooked the dusty roads around the Pantanal arena, threatening a high near 95 degrees Fahrenheit (35 degrees Celsius). Workers were still scrambling on Friday morning to install air conditioning and carpets, just hours ahead of the Chile vs Australia match.
Across the country, however, Brazilians' famous hospitality and good cheer were already overwhelming the rocky preparations in the minds of visiting fans.
"It has been amazing, people have been so nice to us," said Alvaro Roman, one of thousands of Chileans who had flown or driven across the continent to see the game in Cuiaba. "Brazil is a magical place!" (Additional reporting by Andrew Cawthorne in Belo Horizonte, Michael Kahn in Natal, Steve Keating in Porto Alegre, Philip O'Connor in Recife, Mary Milliken in Cuiaba and Brian Winter in Sao Paulo; Editing by Todd Benson and Kieran Murray)