Reading is the only hobby I can speak of.
读书是我唯一值得一提的爱好。
Obviously I can't speak for other people, but certainly no one I know would entertain the idea.
我显然不能代表其他人的意见，可是我认识的`人当中肯定没有人会有这样的想法。
I can't speak English fluently as I am out of practice.
我不能流利地说英语，因为我已荒疏了。
I can't speak fluently among strangers.
和陌生人在一起，我讲话不流畅。
I think you can always speak english.
我认为你总可以说英语嘛。