I live in Spain but I am far away from being a native speaker. My kids are but they came here when they were young.
I think that it goes without saying that adding Spanish would be a good thing, after all in the Western world it is the second language next to English, but I have just one word of warning. Do not expect to get anything very useful from the web based translators. It is so easy to get reversed meanings. Pick a post from this forum, use the net to translate it to Spanish or other language and then translate the result back to English and you'll see what I mean. As a result I think that the Spanish and English sections would tend to remain apart with little cross talk. People from each side would soon tire of the effort and poor results of Google translate etc.
Jon, I think that you should go ahead. A lack of cross talk is not a reason not to.