Here's another option - rather than upload a cert, try pulling your management cert out of your publishsettings file and using the X509Certificate's constructor that takes a byte[]. Then, pass that parameter the result of a call to Convert.FromBase64String, passing it the string representation of your management certificate from your publishsettings file.
Also, take a look at the Compute management client rather than the Cloud Service Management client. There are more features specific to the compute stack in that client at this time. The code below is a demonstration of such an approach. Note, my _subscriptionId and _managementCert fields are both strings, and I just hard-code them to the values from my publishsettings file as I described above.
public async static void ListVms()
{
using (var client = new ComputeManagementClient(
new CertificateCloudCredentials(_subscriptionId,
new X509Certificate2(Convert.FromBase64String(_managementCert)))
))
{
var result = await client.HostedServices.ListAsync();
result.ToList().ForEach(x => Console.WriteLine(x.ServiceName));
}
}