Been trying to play this game recently now that I have an Android phone, but the weather hasn't been the best for walking around town. I do have a question though, when your XM fills up, you're unable to pick up anymore, correct? So, what do you use that XM for? There aren't any portals in my area, so I really don't have a whole lot to go off of here.
There are areas near me that are of significant historical value, and I noticed on one spot there have to be a hundred portals all linked together within maybe a few hundred yards of each other. Turns out they are all at the Air Force Museum, which is about a half mile north of me. Head to museums and you'll hit the jackpot, unless someone else has beaten you to it.
EDIT: Oh, I'm Sylon on there, Resistance.