Zion National Park
AZion National Park: What's the best time of year to hike in Zion?
I would second Greg's answer that if you go in late August/September you can hike comfortably at the beginning of the day and it only starts getting hot in the afternoon. Being cold would not be a concern at this time of year.
AQuito: Time crunch must do/see/eat in Quito?
I would go to the top of Basilica del Voto Nacional. I would also highly recommend going up Teleferico (cable car that takes you above the treeline and offers great views of the city with some light hiking at the top).