My decals were coming of my 2006 Allegro Open Road. They were especially bad on my passenger side cargo lids. As a master of incrementalism, I removed the old decals with a hair dryer. You just get it started and then you pull with the hair dryer behind your work.
I then cleaned all the dirt and glue off with iso alcohol using rubber gloves and a rag. I used frog tape where the old lines of the decal were and masked the other 12 to 18 inches with blue tape and newspapers.
Here is the best part. I repainted the old area of the decals with Rust-Oleum Universal Forged Hammer Paint and Primer, Burnished Amber.
It almost exactly matches the color and texture of the old decals. I bought the paint at Home Depot for about $8.00. The clerk warned me of the 30 minute to 2 hour recoating time or 7 DAYS, which is in the fine print. I will be doing more of this as the decals fall off. I think this is much better than new decals, and it costs very little. This project turned out great.