Google's John Mueller responded to a question in Google Webmaster Help with familiar advice. Build one great site, as opposed to building many smaller sites.
I'd recommend focusing on a single website, instead of this collection of sites that you have now. In particular, I'd make sure that your single website is of the highest quality possible, that it contains unique (not rewritten / spun / reprocessed) content, content that's relevant to the users of your site and compelling to them. Don't keep this collection of low-quality sites, it's really much better overall to focus on making a single fantastic site instead.
This is common advice he has given before.
He even said so with location specific sites.
So if you have a strategy that involves multiple sites - make sure you have enough quality to go around.
Forum discussion at Google Webmaster Help.
Image credit to BigStockPhoto