Dallas G. is correct that Mary is the sweetest woman on Earth but she's picky about who she befriends so you can't just be a douche and try to be funny right off the bat. She will shoot you down unless you're Richard Pryor or something. I didn't speak to her for the first 7 years I went to Joni's. That's paying dues people! Just order the breakfast burrito, know what you want on it, and move out of the way. Do that for 5 or 6 years and then try talking to Mary. Tell her your name to start and ask how her day is. Give her some sugar or things won't go well for you...and by sugar I don't mean a kiss, just sweetness.
I was sad to hear that her partner in crime Jose left, they were like the Burt and Ernie of the cafeteria world. Jose's tamales (special order only during the holidays) rocked the house..I also feel like a piece of Mary left when Jose did. Sad times.
A couple of more tips--
A. Don't try to order something crazy like the Denver omelette...it's on the menu but just don't order it. Mary will have to get weird ingredients out that aren't in her immediate reach. She's getting up there in age and I don't want her to get hurt so just do what I say.
2. There is a small window area where the food that is ready is placed. Don't stand in the window area unless you know your order is there ready for you. There are people behind you, standing out of the way that need to get to their food. MOVE!
C. There are two places to order food, the grill (where the awesome Mary works) and the sandwich bar...you don't have to stand in the grill line if you want a sandwich, just cut past everyone waiting for the grill and order you sandwich.
Stick to that and everything else will be cream cheese!