English or Deutsch?

I am no where close to being fluent in German yet. But, I often have this question in my head, should I try to speak in German with this person? Can I do it? Will they be patient? Do I know enough of the words I need?

Occasionally I speak this great form of 'Germglish', but it hurts even my ears to hear it (it's worse than spanglish!). 

So I try to go for the all or nothing approach. I SHOULD always try German, and I do- mostly. But then I need help with a word, and all of the sudden the conversation I was attempting and halting through is happening in English! What just happened? 

And even when a conversation is in English, I find myself searching for the correct English word to use, not that I know the German word for what I want to say, but I can not think of the English one either! And sometimes I can understand what someone is saying in German, but could not translate it into English. 

So, I have definitely feel like a baby, with the trouble of knowing what I want to say, but not having the words to express myself. But I haven't thrown an temper tantrums- yet. I guess that will come when I get a little better and feel more like a toddler!