Internally mixed soot / sulfate aerosols are ubiquitous in marine atmospheres, found both in polluted and quite pristine environments. Soot particles become more hydrophilic as they age in the atmosphere, both due to alteration of their surface properties via chemical reaction and to their mixing with inorganics. Were these aerosols to significantly impact aerosol activation during cloud formation, they could be important contributors to indirect radiative forcing because they are so widespread. We use recent observations that quantify the mixing state of soot and sulfate during several field campaigns (e.g., P\'osfai et al., 1999) and measurements of the contact angle of soot with water (Zuberi, 2003) to constrain a model of condensation onto mixed soot sulfate aerosols (Gorbunov and Hamilton, 1997). We use this model in conjunction with a detailed aerosol microphysics model and a constant-speed model of a cloud updraft to consider the impact of these internally mixed aerosols on aerosol activation during cloud activation. Data from the ACE-1, ACE-2, and INDOEX field campaigns are used to form representative aerosol populations, which are used as inputs to the model. We find that soot inclusions increase the fraction of aerosols that activate in the extremely polluted environments observed during the INDOEX campaign, and have little impact in the less polluted or clean environments observed during the ACE-1 and ACE-2 campaigns.