What is the cost of living like in El Salvador? How much would it cost to rent a one bedroom apartment in an upscale neighborhood there?
I think the cost of living in El Salvador is much lower, for example when compared to the US. However, I'm pretty sure that it can vary from place to place within El Salvador. For more detailed information you can refer to the Ministry of Foreign Affairs in your country as Litzki1990 suggested.
I think you can also conduct your own research on Google where you are likely to find accurate information. This
website provides a lot of data about the cost of living in El Salvador. You can check it out for more information.