The USDMXN is breaking lower out of an ascending wedge it had been forming for the month of June. If you notice, the 38% retracement of the spike highs in March to the lows in June come in at the recent highs just above the 23.0000 level.
With stocks continuing to be strong, this could give the EM (emerging market) currencies more of a bid, hence, a lower USDMXN exchange rate. A break below the 22.2700 level may target the 21.5000 level once again.