San Juan, Sept. 17. - At their meeting the Spanish evacuation commissioners agreed to begin the formal withdrawal of their Unes within two days. They will evacúate Lares, San Sebastian and Agualdilla, in the northwest of the isiand, withdrawing towards the capital. Under the armistice they could not withdraw their outposts without permission. Detachments of the Eleventh infantry will occupy this territory and raise the American flag. The abandonment of the other outposts will follow.