MEXICAN!! mine's picking up some Ozzy and Lemmy, the local taxi, and the odd intergalactic broadcast.
On the other hand.....can you shed some light on the Mexican music source? any neighbours playing this close by?
You might want to look at your eath connections maybe even cable replacement (good screening), your power supply, any fluorescent lights/dimmer switches? etc etc
Check your mixer settings.....change a few things with the playback/recording sources.
All these can and will all have an affect on your audio signal through the PC (I do a bit or audio recording as well, and have gigged for a number of years with a full live band....LOT'S of audio quality/bleed issues here).
Try moving the laptop to another location - any...