Translation of doorstep in Spanish

I ran across the bridge to reach the other terminal and asked at the check in counter which connecting flights were still available. I wanted to avoid having to drive into the city at any cost.
I wanted to ask whether you would like to help in another English - Spanish project. The dictionary has around 10,000 -20,000 entries and many of them do not have sample sentences. We need to add sentences to give users more background.
It was a short but nice letter from you. I hope that you had a great vacation. I realize that I should practice at least half an hour a day. Vocabulix helps to learn Spanish vocabulary.