OMG this movie is so unrealistic

I thought that was odd at first too. I read a critic's review that said the time is ambiguous, however the boys mentioned Facebook and some of their slang is a bit too modern. I think it's possible Riley and Nate might not have cell phones due to their background (lack of money). Whereas Adam probably didn't have one because he's a bit sheltered and on a "family vacation", if that makes since. Whatever the reasons, having cellphones is irrelevant to the larger story.

i assumed the area was too remote for reception.

Watching it now and by those video games (around 50') they're in 1988 or something.

The movie takes place in the early 2000s, before smartphone even existed. The first Iphone arrived in 2007.

When the drug dealer shows the tape of the guy jumping off the cliff, the date on the recording is july 19th 2000. So the movie takes place a few years after that.