Select Multiple Entries Data Validation - Linked to Charts

Sorry if my title is unclear...... What i'm trying to do here is select multiple markets from a data validation filter/drop down and have my chart display various Market data in one chart.

I have a traffic selector and a signups selector where you can select a single market to display in the chart. Is it possible to select multiple markets from each selector, so that for example, i can compare two traffic metrics (market 1, market 2) and two signup metrics (market 1, market 2) in one chart?