I don't know if the opening of the Jolly Holiday Bakery has had any effect on Mary Poppin's schedule.
If Bert is at Disneyland Park that day, the two are always together. Generally, look for them on Main Street in the morning. They may stroll to Fantasyland and back later on.
There is no single, fixed location for a meet and greet. They tend to choose a storefront near Town Square (closer to the Park Entrance than not) when they are staying in one place on Main Street.
If the "Stage Shows & Live Entertainment" times guide states that the Disneyland Band will appear at the Main Entrance in the morning, Bert & Mary will often take a stroll down Main Street, coming through the tunnel on the side by the Disney Gallery. They don't participate in the whole show, but stay for a few minutes and then go back to Main Street via the tunnel closer to City Hall.
They do have a show of their own with the Pearly Band in front of the castle. The dates and times are never publicized. It is definitely after noon - 1:30 PM has often been the time. As for days, as I've written before, it seems that the show take place on relatively busy days, and probably always on weekends.
Today, I did not see the show, but they were out at 1:30 by the Wishing Well on the Right side of the Castle.
I do not believe they will be at the Jolly Holiday because they would be mobbed and block traffic at the resturant.
Today, I did not see the show, but they were out at 1:30 by the Wishing Well on the Right side of the Castle.
I do not believe they will be at the Jolly Holiday because they would be mobbed and block traffic at the resturant.