We love the Portland Zoo! We've only gone a handfu...

We love the Portland Zoo! We've only gone a handful of times but each time was a great experience. The staff is friendly and knowledgeable. Weekdays are probably best, although I can't speak for summers. Get there early and pay for all day parking, unless you go there a lot plan on roughly 3-5hours to thoroughly enjoy and see everything.
My only qualms are that the layout isn't my favorite and it gets really congested in the NW animals section, but this isn't the zoos fault. Also as great as it is to have a drink every now and then I was disappointed to see alchol for sale there. We didn't encounter anyone who was overtly drunk, but it makes the zoo a little less family friendly.

Bring a stroller or wagon! Maybe even a snack and definitely water! Rainy days are nice there too (less people).