Myanmar exchange rates fluctuate as always and foreign currency is illegal in Myanmar. It is a kind of hard to tell what the Myanmar exchange rate is today in the market. Myanmar exchange rate is changing every hour by the black market rate. Please don't fallow the rate beside the street, they might say you higher every now and then and changed. They might try to chit you as well on the street beside the park. Try to find someone you trust or better change at the hotel, but the rate might be far lower than Market. But it is safe to
change your money at your hotel. Make sure you count your money when you change, there might be some missing note if you change beside the street or near Maharbandula park beside Sule pagoda.
Make sure you change enough money before you travel around Myanmar from Yangon and Mandalay like big cities. Myanmar exchange rate is always lower if you try to change money in other part of Myanmar.