In my experience, if you are running straight into a Sony portable (i.e. D7, D8, D100, M1) and don't feel comfortable pestering the FOH guy to adjust the feed (not usually the first thing on their mind 10 seconds into a show as you realize your feed is way too hot), then I'd run a pair of -10db XLR attenuators. If you run into a SBM-1 first then IME you shouldn't need the attenuators - YMMV on the SBM-1 but I've never had a problem, wheras I've seen plenty of brickwalled Sbd tapes run straight into a sony portable. Again, it's all a matter of your comfort and ability to pester the FOH guy - some are nice and helpful and some want you to go away and leave them alone, especially at the beginning of a show. As Manny pointed out, I'd definitely advise having a set in your bag of tricks so you can decide on a case by case basis. I bought mine at Leo's Pro Audio in SF (they also have a store in Oakland) and they work great - I like the XLR inline variety myself, rathen then the RCA type but that may just be personal preference.
As long as we're on the subject of what to have with you for a Sbd patch, in addition to the XLRs (make them between 10-20' long so you can get out of the FOH person's way as needed) and attenuators if needed, have a good quality, long set of RCA cables and also a set of RCA>1/4" TS adapters - IME, RCA feeds are fairly rare from Sbds unless you are running out of the line out of someone's deck, but 1/4" feeds are occasionally the only option and I'd advise being preapred for the possibility.