"I’d rather be fishing” is a saying that has been on many items, such as bumper stickers, license plate holders, T-shirts and hats.
The “I’d Rather Be Fishing” bumper sticker existed by at least April 1976, when stickers were handed out free at the Los Angeles (CA) Sportsmen’s Vacation & Travel Show.
9 April 1976, Los Angeles (CA) Times, pt. 3, pg. D11 ad:
Free Bumper Sticker
I’d Rather Be Fishing
9 April 1976, Long Beach (CA) Independent, pg. C4, col. 1 ad:
LOS ANGELES SPORTSMEN’S VACATION & TRAVEL SHOW
Free Bumper Sticker “I’d Rather Be Fishing”
21 April 1976, Lynnwood (WA) Enterprise, “Bumper sticker business is alive and booming” by Marie Botnen, pg. 7, col. 6:
And then there are those messages from people who participate in various sports themselves..."Sailors Have More Fun”, “I’d Rather Be Fishing” or “Skiers Are Better Lovers”.
21 September 1977, Pasadena (CA) Star-News, “If you can read this, you may be too close” by Edwin Schoenler (Knight-Ridder Newspapers), pg. C8, col. 2:
Apparently not all drivers are content. A few Sundays ago within a distance of 30 miles we sighted bumper stickers saying “I’d Rather be Flying,” “I’d Rather be Fishing,” and “I’d Rather be Sleeping.” That “rather” theme could go on forever.
Google News Archive
2 November 1978, Charleston (SC) News and Courier, “Doing The Charleston” by Ashley Cooper, pg. B1, col. 1:
THE CAR in front of me yesterday, in a James Island traffic jam, had a bumper sticker which said, “I’d Rather Be Fishing.”