What date will it be? I'll do a wee sun dance for you...
I have a feeling the road is closed between the roundabout at the end of London Road (or Portobello Rd, as it becomes) and Portobello. So I've drawn a wee route on here.
The only reason I took it down Regent Road rather than Leith Walk is that it's a bit quieter - either will be fine.
http://www.gmap-pedometer.com/?r=2752281 When you get to the end of my route, Google refuses to accept you can cross Sir Harry Lauder Road but there's a pedestrian and bike crossing! Then straight down into Portobello and turn right.
So, using streetview, this is where you turn right off Portobello Road, onto a little lane, Fishwives Causeway:
http://tinyurl.com/c3to8nWhich looks like this:
http://tinyurl.com/c5wbta (I'll ask the man in the stripy jumper to be there)
This is as far as googlemaps will take me on Fishwives Causeway, but if you follow the cyclist in the picture you'll come to the crossing!
http://tinyurl.com/dgn2pkAha - here's the crossing from the far side - if you 'turn round' from here you'll be looking at the road down to Portobello (stay on Fishwives Causeway, not Baileyfield Rd)
http://tinyurl.com/d4dao3(aha - just spotted Judy's directions - that IS a nicer way, and the above is still useful once you get out to London/Portobello road!)