I live in a very French area of Montreal. I also live with my parents, who are primarily francophone. They speak and understand English, but only when necessary (as in, when we don't want DD to understand us).
My DD is 29 months old. She understands and is starting to speak French, and she understands basic Vietnamese.
When she was born, I was still married to my XH, who only spoke English. We agreed on the OLOP technique whereby he would speak English to DD and I would speak French to her. I was essentially relying on him to model English for her.
Now that we are divorced and that he no longer sees DD, she has very little exposure to English, save for a random tv show or hearing me talk to my bf. For a while, I just stopped worrying about teaching her English because her language skills seemed slow to develop. She's just gone through a big language explosion so I'm not as worried about her French acquisition now. Because of the laws in place here, unless I can scrape together enough money for private English school, DD will be forced to attend French school where English instruction is started very late IMO (3rd grade). The point of that is to ensure that French remains the primary language.
I have no problem with DD going to French school and solidifying her knowledge of French. It's a tough language to write, and though it is my primary language, I still struggle with it today. However, I do want DD to become fully bilingual so that she can easily travel and work elsewhere than in Quebec.
I'm wondering if it's a good idea for me to suddenly switch languages on her and only speak to her in English. She'd still have my mother to speak in French to, and my father to speak to her in Vietnamese. Her daycare is exclusively French...I don't want to confuse or alienate her though...
I've also considered putting her in an English kindergarden, if I can find one in our super French neighborhood, or perhaps finding activities for her to do in English.