I've heard that because vegan proteins aren't complete I need to combine different vegan proteins in every meal to ensure I get all the essential amino acids. Is this true?

Protein Combining is a popular myth. In short, you DO need the full range of essential amino acids in your day but not necessarily in every meal. Read the entry on 'High Quality or Complete Protein' here http://www.veganhealth.org/articles/protein#comp. It is also important to note that some vegan protein sources should be considered complete proteins on their own (read this http://jacknorrisrd.com/?p=1180 for some suggestions on how to get the best quality protein).