While you are at Starbucks, or any other of your favorite coffee shops, grab a packet or two of Splanda.
Rip open one packet and carefully sprinkle the contents on one ant mound; do this in such a way that you do not disturb the ants.
The ants will not be alarmed and later will find the 'food' that you left for them; they will carry it down into the inner sanctum.
Everyone will get an ant size stomach ache and decide to move away from the area.
Okay, it's not an all natural solution, but it does work and costs very little, even if you actually buy the box of Splenda.
(I got mine at a yard sale for $1.00 for and entire industrial size box.)
