Spring is normally when Safari West gradually prepares for the busy summer season.

But this year, a stampede of visitors arrived at the African wildlife preserve near Santa Rosa earlier than ever, and shows little signs of letting up.

"This year we were almost sold out every day in March. We've never experienced that before," said Aphrodite Caserta, a spokeswoman for the preserve.

Visitors to Sonoma County spent $1.47 billion in 2011, according to the latest figures released last week by Visit California. That's a 9 percent increase over 2010, and the most on record since 1992, when such data started to be collected.

Industry experts say the trend reflects a better economy, people traveling again and Sonoma County ever-more coming into the national consciousness as a desirable destination.

"Sonoma County is such a hot spot to vacation," said Pauline Wood, who co-owns the KOA Kampgrounds in Petaluma with her husband, Chris. "Very few places have the weather we have and so many things to do when people stay at campsites or hotels."

The increase in visitor dollars, which in 2011 equaled 19 percent of tax revenue generated in Sonoma County, also reflects an average increase in lodging costs.

The average daily room rate in the county rose 3.6 percent last year to $116.80, according to Smith Travel Research, which tracks the sector.

Wood said the Petaluma campground raised rates this year for the first time in three years, a 2 percent increase she said was necessary to offset higher costs to run the site.

She said the price increase hasn't hurt business, however, and that the most explosive growth has been with the site's 20 lodges, which offer such hotel-style amenities as linen service, kitchens and gas-powered grills.

"The glam camping market, where people have an outdoor experience without having to rough it, has really boomed," Wood said.

At Hotel Healdsburg and H2 Hotel, which represent the other end of the lodging spectrum, rates also have increased between $20 and $40 per night since 2011.

Hotel Healdsburg charges visitors $460 a night on summer weekends with a two-night minimum. The hotel is pretty much booked this summer, said Circe Sher, marketing marketing director for both hotels.

She attributed the robust conditions to Healdsburg's burgeoning collection of restaurants, wine shops and galleries, as well as the attention paid to the town by the national media.

Travel and Leisure in April named Healdsburg's plaza one of "America's Most Beautiful Town Squares." The month prior, Fodors.com named the community one of the "10 Best Small Towns in America."

In October, the influential online travel site TripAdvisor ranked Sonoma County as the nation's premier wine destination, and among the top five in the world.

"Obviously, the economy has improved, too," Sher said.

Despite the higher costs on average to stay in Sonoma County, hotel occupancy rates continue to bounce back from recession-era levels.

Occupancy rates rose 6.2 percent last year, filling 67.1 percent of local hotel rooms, according to Smith Travel.

Occupancy rates from Jan. 1 through April of this year were 63.1 percent, compared with 56.7 percent for 2012.

Over the same period, the average daily room rate increased from $98.21 for the first quarter in 2012, to $100.66 this year.

"That's good news. It basically says you (lodging owners) didn't drop rates to get people through the door," said Tim Zahner, chief marketing officer for Sonoma County Tourism.

Tourism employment accounted for nearly 17,000 jobs in Sonoma County, according to Visit California, meaning almost one of every 10 jobs in the county is tied to hospitality and tourism.

From 2001 through 2011, industry earnings generated by tourism spending has increased by 41.5 percent.

Zahner said the bulk of visitors to Sonoma County continue to hail from the West Coast, including from places served by Horizon Airlines, which operates from the county airport.

But he said international travelers increasingly are finding their way here.

Caserta said she expects to see many of them this summer at Safari West, which is in the process of hiring and training more tour guides to meet the peak summer demand.

"We'll be ready," she said.

You can reach Staff Writer Derek Moore at 521-5336 or derek.moore@pressdemocrat.com. On Twitter @deadlinederek.