Personally, I think that the best way to deal with the situation is to let your hosts know with the utmost respect and Derech Eretz that you are religious and then wait to see what their reaction is. If they understood what you are telling them I would hope that they would ask you about Kashrut and what you do and do not eat. If they do not ask you I would suggest that you wait to see how their kitchen is set up. If there is some semblance of Kashrut in the kitchen then you can probably rely on various leniencies so as not to offend them. If they do not keep Kashrut at all then it will mean that you cannot really eat anything that has been cooked in their kitchen. However, in my experience, if they do not keep Kosher at all in their home they may be much more open to trying to accommodate your Kashrut requirements than a family who does keep some of the Laws of Kashrut but not in a Halachic manner.