What is the best solution making global service for S3 and EC2

Im developing global mobile service communicating with back end server ( S3 - file server , EC2 - application server) But i don't know how many s3 and ec2 are needed and where i should launch these. So i'd like to know about below

1. Im planning to mount S3 in Oregon. As you know, CloudFront is the good solution for getting image quickly but the problem i wanna solve is uploading. I thought 2 solutions. The first solution it that using Put method to CloudFront, upload file to S3 through CloudFront. The second solution is mounting several S3 in different regions. Which is the better solution?

2. Now i am developing application server in only one EC2. I might have to mount several EC2s for global service. but i don't know how to make end users to connect to specific ec2 of several EC2s. Can you explain me?

thanks