This should work for you:
([+-]?\d+\.?\d+)\s*,\s*([+-]?\d+\.?\d+)
Online RegexPlanet Demo: http://fiddle.re/20pm
This permits any coordinate to be a number which optionally starts with +
or -
. Number can be either integer or double (but dot must be enclosed with digits if present).
Finally, you can get latitude and longitude as group1 and group2.