How poor can your English be? My child in primary school has Japanese and Korean classmates, whose mom can hardly speak English. So far, all communications are mainly by emails or newsletter. And there are only around 3 - 4 times a year that you are ask to go to school to speak with the teacher personally face to face.
If your English is not good, it is true that you are going to have problems with mingling with other parents. There are functions and getherings that you can probably not take part in actively. Like helping out in class outings, helping out at the PTA, etc. Just ask yourself whether you would fee bad about that.
To train up yourself, just watch more English channel. Lots of dramas, like CSI, Ugly Betty are enjoyable.
多口插句咀:
u will have thousands problems need to encounter in the coming years if u have decided to go to IS stream. Your "problem" is really "nothing" to get worried.
i personally don't think you need to worry too much. there'll be 2-3 PTA a year. you can ask your husband to attend the PTA. whether you can mingle with other western parents depend on your character as well. i have seen some japanese mothers can mingle well with other western mothers too, even though the japanese mothers are not the fluent English speakers. and i guess most teachers understand that we are local parents, can't speak perfect English.
don't worry too much and give yourself too much pressure. i think you are such a good mother willing to learn English for your kid.