Combine cheeses with flour and chili powder in a large bowl until well blended.
Halve, seed and cut peppers into thin strips; wash and stem tomatoes; halve, pit and peel avocados; cut into 1-inch cubes.
Cut bread into 1-inch cubes, leaving some crust on each piece.
When ready to serve, rub the garlic along the inside of a ceramic fondue pot or flameproof ceramic baking dish; add beer and heat slowly, just until beer stops foaming and the mixture begins to bubble.
Gradually add cheese mixture a handful at a time, stirring constantly, until cheese is melted and smooth; add hot green peppers. Place pan over a candle warmer and serve on a tray with groups of pepper strips, avocado pieces; bread chunks, cherry tomatoes and corn chips.