There are so many routes between Redmond and Bellevue that it isn't even funny. Some of them are less populated than others, so depending on how comfortable you are riding with traffic that will be the big factor in deciding your route.
I ride in Bellevue quite often. With all the construction going on there right now, the best advice I can give you is to make sure you've got good tires! You said your route takes you from Lake Sam to the 520/405 exchange. Where about on Lake Sam? It's about 25 miles to circle the lake completely, so are you at the north end of the lake by Marymoor Park, the east side in Sammamish, south in Issaquah, or right on the Bellevue side of the lake? That will be a huge influence on your route.
If you give me a start and an ending street, I can give you at least 3 good routes to take.
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"I feel like my world was classier before I found cyclocross."
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