If you wrote .NET C# code for InfoPath project, the resulting dll will be bundled with the InfoPath template XSN that you publish to the SharePoint site. To programmatically Print, you need Full Trust, so you'll have to digitally sign the XSN with a certificate and users will have to trust that certificate. If so, it should work and print to their default printer (assuming your code doesn't hardcode the printer location).
Patrick Halstead
Project Manager at Qdabra