Unless this keyboard is a custom style (gaming, split hand, etc) I would suggest just replacing it. The cost of a new USB keyboard can be below $10US. Compared to the cost of purchasing alcohol and the time spent disassembling, cleaning and reassembling the keyboard, I think it would be well worth the price. Search sites like Amazon, NewEgg or Ebay for cheap keyboards.
If it's a special/non-replaceable keyboard, or you are set on going with the cleaning method, keep these tips in mind. Isopropyl alcohol is only really necessary if you are not going to remove all of the electronics first (because the alcohol is less likely to damage them). If you are using it, you should aim for high % of alcohol (90% or greater, the rest is water). This can be found in most drugstores or grocers with a personal care section.
If you are going to remove the electronics, you can wash using water and mild detergent, as long as you dry it thoroughly before reassembling. The suggested rice method is a good way to remove the water quickly. After removing the electronics, whether you decide to remove all the keys is up to you, but it would get cleaner with them removed. Use caution with large keys such as the space bar, shift and enter, as these often have springs or support bars that can be bent or broken if not removed carefully.