Currently, the nations and regions that Elsword supports is larger than the areas that HeroWarz supports. You can check the HeroWarz FAQ, specifically the Technical Questions area to find out where is supported. Right now, the US and Canada, Australia, New Zealand, and much of Europe are able to access. While Puerto Rico is technically a US territory, it appears that it does not count as part of the area accepted into the current server. Customer Support may have an answer for why that is, so you might want to send in a ticket to them to ask.
If your friend would like to be kept up to date, I'd recommend following the HeroWarz Facebook page. Several people ask on that page when certain countries or areas will be allowed to play, and the response generally states that they will announce it on social media when that happens.