I actually found this place on a random fluke. I was eating at a nearby restaurant and my constant companion remarked that he'd never eaten Venezuelan food before, so we should come back and try this place. Since then I've been to Viva Las Arepas several times -- usually with visitors in tow. It's one of my favorites and a nice find on the North end of the Strip. My favorite is the chicken Arepa (with cheese, dripping in the creamy cilantro sauce). It's my favorite because the chicken tastes of this fantastic smokey flavor I've not found elsewhere in Vegas. I've also had their whole chicken (a favorite with my constant companion) and the meat just melts in your mouth.
Is it a healthy choice for your stay in Las Vegas? Probably not. However, it is likely one of the most delicious. I once took my fabulously unadventurous younger brother here, and he and his friends absolutely loved it.
To address concerns raised by other visitors -- yes the restaurant itself is not in a particularly glitzy part of town; however, it is in an area that is in the process of being revitalized. The restaurant is clean and well kept, and I've never had any problems in the neighborhood. The food is worth it! I have plans to go back in the near future.