The portfolio is not just about pretty renderings.
Max takes quite some time to master. You should learn it, just because most employers want someone who knows their way around a 3D modeling program. But have you tried making models in Autocad? I personally find it a lot easier to build models (as long as it is orthagonal) on Autocad and then importing them to Max for mapping, lighting and rendering. You can google tutorials for lighting, materials and rendering pretty easily.

Also, learn Photoshop or Illustrator. You will need it to make layouts and to touch up renderings. They are pretty intuitive programs, so it shouldn't take you too long to learn the basics to get simple things done.

But, if you're pressed for time to make your portfolio, why not include hand drawings and sketches. Show the process of how your projects came to be through analytical drawings. You can also include artwork and photography.

Medusa makes a good point. I know of at least one archinecter who was just accepted to a good grad school with a portfolio of absolutely no "architecture" projects.

Hand drawing, sketching from life, diagrams that are really cool, maps...all those things are portfolio material. And really funky models. Just make stuff in your free time that explores further an idea that the "exercises" you were assigned didn't get into.

Also: it sounds to me, Archilearner, like you could benefit from narrowing your field for applications. Don't make a general portfolio that you send to 20 schools. Think about what areas interest you: sustainable design? structural expression? NURBS? historic renovation? urban design? Then find out what schools seem like a good fit and focus your portfolio towards those ideas.

Having some really bitchin' renderings might look cool, but grad schools want to see someone who can think, not just produce. Rather than focus on making pretty pictures, focus on revealing a thought process.

It's good you are being self-critical - now you have time to work on it! Good luck.