My English is poor.

My spoken English is poor.

I can't speak English well.

My English is not good enough.

My English is terrible.

My English is bad.

I'm sorry, my English isn't that good.

I don't speak much English.

My English is a little rusty.

My English is okay.

My English is not that good.

根据具体的语境和需要，你可以选择其中一句或结合几句来表达你的意思。例如，在正式场合或需要更委婉的表达时，可以选择“My English is not that good.”或“I'm sorry, my English isn't that good.”。在较为随意的交流中，可以使用“My English is terrible.”或“My English is bad.”。