^ No, there is no public observation deck, however, you can have a meal at the revolving restaurant on the top floor of the Crowne Plaza Chateau Lacombe:
www.chateaulacombe.com
Also, unless you really like malls, stay away from WEM. It's really just tacky, unremarkable, and a complete rip-off at filling its only purpose...shopping...
again, unless you have a thing for malls, just skip it, it is out of the way, and rather disappointing.
For the downtown views, you can wander up to Saskatchewan Drive, a road right on the riverbank. It is only a few blocks north of Whyte Avenue and Old Stratchcona...High Level Bridge is also a decent spot for downtown pics....as is The Muttart site in cloverdale.