WordNet sense 1 (full of trivial conversation):

chatty, gabby, garrulous, loquacious, talky

WordNet sense 2 (marked by a ready flow of speech):

voluble

WordNet sense 3 (unwisely talking too much):

bigmouthed, blabbermouthed, blabby

WordNet sense 4 (lacking discretion; injudicious):

indiscreet

WordNet sense 5 (friendly and open and willing to talk):

expansive