Macrobid - The capsules are too big for me to swallow, my Doctor ( through the Nurse) said to open?

That's not an unusual method to take a whopper of a pill, it definately will taste yucky! My doc recommended mixing it into a single cup serving of yogurt not only to help the taste but he told me that the yogurt would aid the absorbtion of the medicine. Good luck! =)

Yes - although it will taste terrible... but will not be harmful. You could try mixing the powder in with a little ice cream or jam to disguise the taste.
If you continue to have difficulty call your doctor or pharmacy. There are suspensions available (Furadantin, Nitrofurantoin).