Look at whatever site, but if it is East wind, it will be ok, if not too light. Something up to 15 knots in gusts I would say will be wind enough to go out.
If it is cloudy it is not good for the thermal. So sunshine and East wind.
Truth is all the forecasts suck and are never right. It's a long story that has lots of speculation surrounding it, like none of the windmeters are in ideal locations. Anyhow, statistically, we have kiteable conditions 300 days per year. This winter has been a little on the crappy side, but I hear it has something to do with el nino or something like that (I really don't know, because I just look at the trees to see if I will be able to kite on a given day). I wrote a blog post about it if you are interested. It has charts and other info based on the past 8 years of data. http://cabaretecondos.com/cabarete-wind/
Kitexcite also has a really good webpage that has documented the conditions based on their personal data from being on the beach for like 10 years. Stafan, the owner, has kept track of it: http://www.kitexcite.com/new-wind-forecast/