More evidence supporting Washington's orthodoxy comes from his friend and speechwriter James Madison. Not to say JM was GW's closest friend, but, they served in government together at the exact same time. JM was in congress the entire term of GW's presidency; 1789-1796. Madison writes in Paul Leicester Ford's book, GW did "not form definite opinions on it [Christianity], but he took these things as he found them existing, and was constant in his observances of worship according to the received forms of the Episcopal Church, in which he was brought up."
This is quite interesting as JM had to have known GW skipped out of Communion in the Episcopal Church for years. Obviously JM understood GW to believe in what the sacrament represents even though he would not take part in Communion.
Many of the testimonies of GW taking communion come from Episcopalians; Jonathan Mitchell Sewall, Alexander Hamilton's wife, and GW's adopted daughter Nelly Custis-Lewis. After the revolution, GW shied away from communion in the Episcopal Church. The evidence supporting GW taking communion is at least 80-20, probably 90-10 in favor.