Laredo, Texas (CNN) -- The hardened dirt road turns off Highway 359 and runs under a simple iron archway. It's an easily forgettable entryway into one of the nation's poorest neighborhoods, the San Carlos "colonia" on the outskirts of this Texas border town.
When you cross, it's like entering a different world.
Anabeli Rendon, a 14-year-old high school freshman, stands outside a dilipated orange cinder-block shed where she lived with her mother and young sister just a couple years ago. They had to run an extension cord from a nearby house to get electricity.
"At first I didn't like it," she says. "My mom didn't have enough money to get a big house, so it's hard."
A colonia is a cluster of homes built on some of the most undesirable property along the southern border. Many colonias lack basic necessities like electricity, water and sewage lines.
It's estimated 400,000 people live like Anabeli in colonias along the southern U.S. border. But the exact number is difficult to discern. Many residents, in the United States illegally, fear being deported if they participate in the census.
"If the president asked me for your Census form, I can say, 'No, you can't get it,' " Robert Groves, the 2010 Census director, told residents.
Groves recently toured hard-hit communities to try to ease those concerns, telling residents that participating in the census could lead to better communities with paved roads, more electricity and improved schools. An estimated $400 billion will be dispersed around the country based on census results.
"The benefits of participating in the census are quite large," said Groves. "If you get counted, you get your fair share of that money."
The people who live in San Carlos are on the fringe. Colonia experts say most make less than $10,000 a year and are constantly searching for day work. Anabeli's mother sells plates of food in the neighborhood. The young girl doesn't hear much from her father, who lives in Mexico.
"If you look around, it's third-world conditions," says U.S. Rep. Henry Cuellar, D-Texas.
The San Carlos colonia sits in his congressional district.
Rep. Cuellar escorted Groves on the tour of the border colonias. The two are on a mission to build trust, trying to assure residents they should participate in the census.
Officials blame language barriers, haphazard housing and "complex and fluid households" for the difficulty in getting an accurate count of the population. Perhaps the biggest obstacle, they say, is a deep-seeded mistrust in the communities of Census counters.
Many families in the colonias have family members living in the United States illegally. There's a fear census data will be used to identify and deport illegal immigrants.
Anabeli is a U.S. citizen but, she says, some of her relatives are living here illegally.
"I think they're scared. Most people here are immigrants," said Anabeli, who has moved from makeshift home to makeshift home since she was 3.
U.S. Census officials say the population in the colonias was dramatically undercounted in the 2000 census.
To increase participation in the border colonias this time, Groves says the census form will be printed in English and Spanish. Census workers also will canvas the streets on foot, knocking on doors asking people to answer the 10 questions on the census form.
But in a community where the hunt for water is a daily struggle, government officials acknowledge joining in the census process is the farthest thing from the minds of residents.
Anabeli's mother quietly listened to the congressman and the census director but minutes later she was back at her home. The family is moving again, just across the street into a small two-room house, which rents for $200 a month.
Five people will live in the 264-square-foot space. There's no air conditioning or heat; a shoddy bathroom sits outside the house.
As Anabeli's mother carried a few belongings into her new home, she said her fears of the census had been eased and that she would let herself be counted.
"If they get it right ... that will help improve the overall community," said Rep. Cuellar.