No one – well, certainly not I – is suggesting you go out and talk to strangers on the street with only basic, prepared sentences, the reply to which will be awkwardly incomprehensible.
What I’m advocating is that even after a few days or weeks of acquiring basic sentence models that you can play with and adapt, and which give you insight into how the language actually works (negative, present, past, subject, object, word order, etc.), you should attempt to use that knowledge at every reasonable opportunity, namely with people you meet in appropriate social contexts such as friends, friends of friends, language partners, tutors, etc. You should seek and create such social opportunities, and you shouldn’t skip on any opportunity to use the language. Even if it implies possibly making a fool of yourself, even if you may not get the answer.
The idea that you shouldn’t speak until you know you can understand the reply is excessively prohitibitive – you never know what answer you’ll be getting and the possibility that you won’t understand is ALWAYS there. It will there in 6 months, and it will still there in 2 years. If you don’t understand, say it. People will repeat or rephrase; it’s not rude, and most people appreciate anyone trying hard to learn their language – in the appropriate context, of course.
If you can, take the time to prepare mentally for upcoming social events by looking up the words you think you’ll need and try to anticipate eventual replies. This way, you focus on the way the language is actually used in the real world.
I understand Steve’s message that you shouldn’t worry about the details and that you should do whatever brings you pleasure in your study, and I’m not suggesting you ignore that by any means, but most people also hope to reach a reasonable level in a reasonable amount of time, and the reality is that most people struggle to reach fluency. I can’t see how delaying speech can help acquire fluency faster, but I suppose that isn’t on top of everyone’s priority list.