Only been to the old one Proper shithole - although not quite as knackered and decrepit as the Nou Camp.
Yes went earlier this year as part of a trip that also included the Nou Camp and Barcelona city. It took us about 15 minutes to get from the city centre to Espanyols ground. I'd say its about 4 or 5 miles from the city centre.
If its the olympic one where England played Andorra... then yes. Up the top of a mountain l recall, we got a bus back into the centre that were waiting for the England fans. Wouldn't like to think l was walking it.
No I've been to the Olympic Stadium before ,Espanyol moved into a new stadium at the beginning of the season